Synthesis of 3-deazapurines

ABSTRACT

This invention relates to compounds based on the 3-deazapurines ring system and to methods for making such compounds. The invention also generally relates to the field of &#34;antisense&#34; agents, agents that are capable of specific hybridization with a nucleotide sequence of an RNA. The 3-deazapurine-containing compounds of this invention can be useful for modulating the activity of RNA when incorporated into oligonucleotides. Oligonucleotides and their analogs are used for a variety of therapeutic and diagnostic purposes, such as treating diseases, regulating gene expression in experimental systems, assaying for RNA and for RNA products through the employment of antisense interactions with such RNA, diagnosing diseases, modulating the production of proteins and cleaving RNA in site specific fashions.

This application is a divisional of U.S. patent application Ser. No.08/514,762 filed Aug. 14, 1995, now U.S. Pat. No. 5,587,470, which is adivisional of U.S. patent application Ser. No. 08/027,011 filed Mar. 5,1993, now U.S. Pat. No. 5,457,191, the disclosures of which are herebyincorporated in their entirety.

BACKGROUND OF THE INVENTION

This invention relates to compounds that have utility as oligonucleotideintermediates, and to methods for making such compounds. The compoundsare based on the 3-deazapurine core. The invention also generallyrelates to the field of "antisense" agents, agents that are capable ofspecific hybridization with a nucleotide sequence of an RNA. Inparticular, this invention relates to novel compounds that may beincorporated into oligonucleotides, these compounds include novelheterocyclic bases, nucleosides, and nucleotides. When incorporated intooligonucleotides, the 3-deazapurines of the invention can be useful formodulating the activity of RNA. Oligonucleotides are used for a varietyof therapeutic and diagnostic purposes, such as treating diseases,regulating gene expression in experimental systems, assaying for RNA andfor RNA products through the employment of antisense interactions withsuch RNA, diagnosing diseases, modulating the production of proteins,and cleaving RNA in site specific fashions.

It is well known that most of the bodily states in mammals includingmost disease states, are effected by proteins. Such proteins, eitheracting directly or through their enzymatic functions, contribute inmajor proportion to many diseases in animals and man. Classicaltherapeutics has generally focused upon interactions with such proteinsin efforts to moderate their disease causing or disease potentiatingfunctions. Recently, however, attempts have been made to moderate theactual production of such proteins by interactions with molecules thatdirect their synthesis, intracellular RNA. By interfering with theproduction of proteins, it has been hoped to effect therapeutic resultswith maximum effect and minimal side effects. It is the general objectof such therapeutic approaches to interfere with or otherwise modulategene expression leading to undesired protein formation.

One method for inhibiting specific gene expression is the use ofoligonucleotides and oligonucleotide analogs as "antisense" agents. Theoligonucleotides or oligonucleotide analogs complimentary to a specific,target, messenger RNA (mRNA) sequence are used. A number of workers havereported such attempts. Pertinent reviews include Stein, et al., CancerResearch, 1988, 48, 2659-2668; Walder, Genes & Development, 1988, 2,502-504; Marcus-Sekura, Anal. Biochemistry, 1988, 172, 289-295; Zon, J.Protein Chemistry, 1987, 6, 131-145; Zon, Pharmaceutical Res., 1988, 5,539-549; Van der Krol, et al., BioTechniques, 1988, 6, 958-973; andLoose-Mitchell, TIPS, 1988, 9, 45-47. Each of the foregoing providebackground concerning general antisense theory and prior techniques.

Thus, antisense methodology has been directed to the complementaryhybridization of relatively short oligonucleotides and oligonucleotideanalogs to single-stranded mRNA or single-stranded DNA such that thenormal, essential functions of these intracellular nucleic acids aredisrupted. Hybridization is the sequence specific hydrogen bonding ofoligonucleotides or oligonucleotide analogs to Watson-Crick base pairsof RNA or single-stranded DNA. Such base pairs are said to becomplementary to one another.

Prior attempts at antisense therapy have provided oligonucleotides oroligonucleotide analogs that are designed to bind in a specific fashionto--which are specifically hybridizable with--a specific mRNA byhybridization. Such oligonucleotide and oligonucleotide analogs areintended to inhibit the activity of the selected mRNA--to interfere withtranslation reactions by which proteins coded by the MRNA areproduced--by any of a number of mechanisms. The inhibition of theformation of the specific proteins that are coded for by the mRNAsequences interfered with have been hoped to lead to therapeuticbenefits.

A number of chemical modifications have been introduced into antisenseagents--oligonucleotides and oligonucleotide analogs--to increase theirtherapeutic activity. Such modifications are designed to increase cellpenetration of the antisense agents, to stabilize the antisense agentsfrom nucleases and other enzymes that degrade or interfere with theirstructure or activity in the body, to enhance the antisense agents'binding to targeted RNA, to provide a mode of disruption (terminatingevent) once the antisense agents are sequence-specifically bound totargeted RNA, and to improve the antisense agents' pharmacokinetic andpharmacodynamic properties. These modifications are designed to enhancethe uptake of antisense agents--oligonucleotides and oligonucleotideanalogs--and thus provide effective therapeutic, research reagent, ordiagnostic uses.

Initially, only two mechanisms or terminating events have been thoughtto be operating in the antisense approach to therapeutics. These are thehybridization arrest mechanism and the cleavage of hybridized RNA by thecellular enzyme, ribonuclease H (RNase H). It is likely that additional"natural" events may be involved in the disruption of targeted RNA,however. These naturally occurring events are discussed by Cohen inoligonucleotides: Antisense Inhibitors of Gene Expression, CRC Press,Inc., Boca Raton, Fla. (1989).

The first, hybridization arrest, denotes the terminating event in whichthe oligonucleotide inhibitor binds to the target nucleic acid and thusprevents, by simple steric hindrance, the binding of essential proteins,most often ribosomes, to the nucleic acid. Methyl phosphonateoligonucleotides, Miller, et al., Anti-Cancer Drug Design, 1987, 2,117-128, and α-anomer oligonucleotides are the two most extensivelystudied antisense agents that are thought to disrupt nucleic acidfunction by hybridization arrest.

The second "natural" type of terminating event is the activation ofRNase H by the heteroduplex formed between the DNA type oligonucleotideor oligonucleotide analog and the targeted RNA with subsequent cleavageof target RNA by the enzyme. The oligonucleotides or oligonucleotideanalogs, which must be of the deoxyribose type, hybridize with thetargeted RNA and this duplex activates the RNase H enzyme to cleave theRNA strand, thus destroying the normal function of the RNA.Phosphorothioate modified oligonucleotides are the most prominentexample of antisense agents that are thought to operate by this type ofantisense terminating event. Walder, et al., in Proceedings of theNational Academy of Sciences of the U.S.A., 1988, 85, 5011-5015 andStein, et al., in Nucleic Acids Research, 1988, 16, 3209-3221 describethe role that RNase H plays in the antisense approach.

To increase the potency via the "natural" termination events the mostoften used oligonucleotide modification is modification at thephosphorus atoms. An example of such modifications include methylphosphonate oligonucleotides, where the phosphoryl oxygen of thephosphorodiester linking moiety is replaced or the nucleotide elementstogether are replaced, either in total or in part, by methyl groups.Other types of modifications to the phosphorus atom of the phosphatebackbone of oligonucleotides include phosphorothioate oligonucleotides.The phosphorothioate modified oligonucleotides are thought to terminateRNA by activation of RNase H upon hybridization to RNA althoughhybridization arrest of RNA function may play some part in theiractivity. Backbone modifications are disclosed as set forth in U.S.patent applications assigned to a common assignee hereof, entitled"Backbone Modified Oligonucleotide Analogs," Ser. No. 703,619 and"Heteroatomic Oligonucleotide Linkages," Ser. No. 903,160, thedisclosures of which are incorporated herein by reference to disclosemore fully such modifications. Phosphoroamidites have been disclosed asset forth in an application having U.S. application Ser. No. 918,362 andassigned to a common assignee hereof, entitled "Improved Process forPreparation of 2'-O-Alkylguanosines and Related Compounds," thedisclosures of which are incorporated herein by reference to disclosemore fully such modifications.

All applications of oligonucleotides and oligonucleotide analogs asantisense agents for therapeutic purposes, diagnostic purposes, andresearch reagents require that the oligonucleotides or oligonucleotideanalogs be synthesized in large quantities, be transported across cellmembranes or taken up by cells, appropriately hybridize to targeted RNAor DNA, and subsequently terminate or disrupt nucleic acid function.These critical functions depend on the initial stability ofoligonucleotides and oligonucleotide analogs toward nucleasedegradation.

A serious deficiency of unmodified oligonucleotides for these purposes,particularly antisense therapeutics, is the enzymatic degradation of theadministered oligonucleotides by a variety of intracellular andextracellular ubiquitous nucleolytic enzymes, hereinafter referred to as"nucleases." It is unlikely that unmodified, "wild type,"oligonucleotides will be useful therapeutic agents because they arerapidly degraded by nucleases. A primary focus of antisense research hasbeen to modify oligonucleotides to render them resistant to suchnucleases. These modifications have heretofore exclusively taken placeon the sugar-phosphate backbone, particularly on the phosphorus atom.Phosphorothioates, methyl phosphonates, phosphoramidites, andphosphorotriesters (phosphate methylated DNA) have been reported to havevarious levels of resistance to nucleases. Backbone modifications aredisclosed as set forth in U.S. patent applications assigned to a commonassignee hereof, entitled "Backbone Modified Oligonucleotide Analogs,"Ser. No. 703,619 and "Heteroatomic Oligonucleotide Linkages," Ser. No.903,160, the disclosures of which are incorporated herein by referenceto disclose more fully such modifications.

Other modifications to "wild type" oligonucleotides made to enhanceresistance to nucleases, activate the RNase terminating event, andenhance the RNA-oligonucleotide duplex's hybridization propertiesinclude functionalizing the nucleoside's naturally occurring sugar.Sugar modifications are disclosed as set forth in PCT Applicationassigned to a common assignee hereof, entitled "Compositions and Methodsfor Detecting and Modulating RNA Activity and Gene Expression," PCTPatent Application Number PCT\US91\00243, International PublicationNumber WO 91/10671, the disclosures of which are incorporated herein byreference to disclose more fully such modifications.

Other synthetic terminating events, as compared to hybridization arrestand RNase H cleavage, have been studied in an attempt to increase thepotency of oligonucleotides and oligonucleotide analogs for use inantisense diagnostics and therapeutics. Thus, an area of research hasdeveloped in which a second domain to the oligonucleotide, generallyreferred to as a pendant group, has been introduced.

The pendant group is not involved with the specific Watson-Crickhybridization of the oligonucleotide or oligonucleotide analog with theMRNA but is carried along by the oligonucleotide or oligonucleotideanalog to serve as a reactive functionality. The pendant group isintended to interact with the mRNA in some manner more effectively toinhibit translation of the mRNA into protein. Such pendant groups havealso been attached to molecules targeted to either single or doublestranded DNA. Such pendant groups include, intercalating agents,cross-linkers, alkylating agents, or coordination complexes containing ametal ion with associated ligands. A discussion of pendant groups is setforth in PCT Application assigned to a common assignee hereof, entitled"Compositions and Methods for Detecting and Modulating RNA Activity andGene Expression," PCT Patent Application Number PCT\US91\00243,International Publication Number WO 91/10671, the disclosures of whichare incorporated herein by reference in order to disclose more fullysuch modifications.

Prior approaches using cross-linking agents, alkylating agents, andradical generating species as pendant groups on oligonucleotides forantisense diagnostics and therapeutics have several significantshortcomings. The sites of attachment of the pendant groups tooligonucleotides play an important, yet imperfectly known, part in theeffectiveness of oligonucleotides for therapeutics and diagnostics.Prior workers have described most pendant groups as being attached to aphosphorus atom which affords oligonucleotide compositions with inferiorhybridization properties. Prior attempts have been relativelyinsensitive, that is the reactive pendant groups have not beeneffectively delivered to sites on the messenger RNA molecules foralkylation or cleavage in an effective proportion. Moreover, even if thereactivity of such materials were perfect, (i.e., if each reactivefunctionality were to actually react with a messenger RNA molecule), theeffect would be no better than stoichiometric. That is, only one mRNAmolecule would be inactivated for each oligonucleotide molecule. It isalso likely that the non-specific interactions of oligonucleotidecompositions with molecules other then the target RNA, for example withother molecules that may be alkylated or which may react with radicalspecies, as well as self-destruction, not only diminishes the diagnosticor therapeutic effect of the antisense treatment but also leads toundesired toxic reactions in the cell or in vitro. This is especiallyacute with the radical species that are believed to be able to diffusebeyond the locus of the specific hybridization to cause undesired damageto non-target materials, other cellular molecules, and cellularmetabolites. This perceived lack of specificity and stoichiometric limitto the efficacy of such prior alkylating agent and radicalgenerating-types of antisense oligonucleotide compositions is asignificant drawback to their employment.

Reactive functionalities or pendant groups attached to oligonucleotidecompositions previously described in the literature have been almostexclusively placed on a phosphorus atom, the 5-position of thymine, andthe 7-position of purines. A phosphorus atom attachment site can allow areactive group access to both the major and minor grooves. However,internal phosphorus modification results in greatly reduced heteroduplexstability. Attachments at the 3' and/or 5' ends are limiting in thatonly one or two functional groups can be accommodated in theoligonucleotide compositions. Such placement can interfere withWatson-Crick binding. Further, functionalities placed in the 5-positionor 7-position of bases, pyrimidine and purine, respectively will residein the major groove of the duplex and will not be in proximity to theRNA 2'-hydroxyl substrate. The 2'-hydroxyl is the "trigger" point forRNA inactivation, and thus, any reactive functionalities must be inappropriate proximity to the receptive substrate located in the targetedRNA, especially the most sensitive point, the 2'-hydroxyl group.

Targeted RNA is inactivated by formation of covalent links between amodified oligonucleotide and the RNA 2'-hydroxyl group. A variety ofstructural studies such as X-ray diffraction, chemical reaction, andmolecular modeling studies suggests that the 2'-hydroxyl group of RNA ina duplex or heteroduplex resides in the minor groove.

The half life of the perfectly formed duplex will be greatly effected bythe positioning of the tethered functional group. Inappropriatepositioning of functional groups, such as placement on the Watson/Crickbase pair sites, would preclude duplex formation. Other attachment sitesmay allow sequence-specific binding but may be of such low stabilitythat the reactive functionality will not have sufficient time toinitiate RNA disruption.

Approaches to perfect complementation between modified oligonucleotidesor oligonucleotides and targeted RNA will result in the most stableheteroduplexes. This is desired because the heteroduplex must have asufficient half life to allow the reactive or non-reactivefunctionalities of this invention to initiate the cleavage or otherwisedisruption of RNA function. The minor side or minor groove of theduplexes formed between such oligonucleotides or modifiedoligonucleotides and the targeted RNA has been found to be the greatlypreferred site for functional group activity.

Therefore, functionalities placed on sequence-specific oligonucleotidecompositions (via modified nucleosides) should preferably reside in theminor groove formed between the oligonucleotide composition and thetargeted RNA, not interfere with duplex formation or stability, andinitiate cleavage or disruption of the RNA. Accordingly, there remains agreat need for antisense oligonucleotide compositions that are capableof improved specificity and effectiveness both in binding and in mRNAmodulation or inactivation without the imposition of undesirable sideeffects.

It has now been found that certain positions on the nucleosides ofdouble stranded nucleic acids are exposed in the minor groove and may besubstituted without affecting Watson-Crick base-pairing or duplexstability. Reactive or non-reactive functionalities placed in thesepositions can best initiate cleavage and destruction of targeted RNA orinterfere with its activity.

The functionalities point of attachment to the base units, which in turnmay be converted to modified oligonucleotide, is critical in the designof compositions for sequence-specific destruction or modulation oftargeted RNA. The functionalities must not interfere with Watson-Crickbase pair hydrogen bonding rules, as this is the sequence-specificrecognition/binding factor essential for selection of the desired RNA tobe disrupted. Further, the functionalities should improve theoligonucleotides compositions' pharmacokinetic and/or pharmacodynamicproperties, as well as the oligonucleotide compositions' transportproperties across cellular membranes. The present invention addressesthese, as well as other, needs by presenting novel oligonucleotideintermediates based on the core structure of 3-deazapurines.

The synthesis of the 3-deazaguanine core is known, Cook, et al., J. Am.Chem. Society 1975, 97, 2916; Cook et al., J. Med. Chem. 1978, 21, 1212.3-deazaguanine is a potent guanine antimetabolite with significantantitumor, antiviral, antibacterial and antiparasitic activities. Thecorresponding nucleoside, 2'-deoxy-3-deazaguanosine, has exhibited awide spectrum, Revankar, et al., J. Med. Chem., 27, 1389, 1984, ofantiviral and antitumor activity in addition to antibacterial activityagainst E. coli, Burman, et al., Chem. Scripta 1986, 26, 15. Workershave made certain modifications to 3-deazaguanine (6-aminoimidazo4,5-c!pyridine) and the corresponding nucleoside2'-deoxy-3-deazaguanosine(6-amino-1-(2-deoxy-β-D-erythro-pentofuranosyl)) imidazo4,5-c!pyridin-4(5H)-one resulting in a wide modulation of theheterocyclic ring system's biological activity. See, e.g., Hartman, etal., J. Labelled Compd. Radiopharm. 1985, 23, 35 (ring modifications);Revankar, et al., J. Med. Chem. 1984, 27, 1389 (peripheralmodifications); Cook, et al., J. Org. Chem. 1978, 43, 289 (same);Revankar, supra (sugar modifications). Workers have attached certaintether functionalities to the 3-position of 3-deaza-adenine. TheChemistry of Heterocyclic Compounds, A. Weissberger, Ed., Imidazole andDerivatives, Part 1, Interscience, N.Y. (1953). However, there has beenno investigation into the synthesis of 3-C substituted deazaguanine. Thepresent invention is the first to set forth substitutions at the 3-Cposition of 3-deazaguanines and 3-deazapurine derivatives.

The bulkiest 3-C deazapurine substituent induces an unnatural3'-endo/high-anti (-sc) conformation of the nucleoside. This preferencefor the anti-conformation may make the 2'-deoxy 3-deazapurines of theinvention enhanced substrates for viral kineses. Further, substitutionsat the C-3 aromatic carbon of the 3-deazapurine ring system are ofinterest because this influences the heterocycle's range of rotationabout the glycosidic bond, Saenger, "Principles of Nucleic AcidStructure," Cantor, C. R., Ed., Springer-Verlag, New York, 1983,potentially modifying biological activity, Saran, et al., Int. J.Quantum Chem. 1984 25, 743; Miles, et al., H.J. Theor. Biol. 1977, 67,499. Further, lipophilic substituents at this position could change thetransport efficiency of heterocyclic bases, heterocyclic base analogs,nucleosides, nucleoside analogs, nucleotides, nucleotide analogs, andoligonucleotides compositions.

SUMMARY OF THE INVENTION

This invention presents novel compounds based on the 3-deazapurine ringsystem that have utility as intermediates for oligonucleotidecompositions. This invention also provides novel synthetic methods forthe preparation of these compounds employing a mild alkylation procedureon an imidazole precursor to this ring system. In particular, thisinvention provides nucleosides, nucleoside analogs, nucleotides,nucleotide analogs, heterocyclic bases, and heterocyclic base analogs.These heterocyclic compounds are adapted for placement of the reactive,RNA cleaving moiety or other reactive moiety into the minor groove siteof the hybrid structure formed from the RNA and the composition throughcareful selection of the attachment of the RNA cleaving moieties.

The compounds of the invention possess unique steric properties thatresult in modified biological activity and better cellular transportproperties for oligonucleotide compositions. These attributes make thesecompositions useful oligonucleotide intermediates.

In one aspect of the invention, the compounds have the formula: ##STR1##wherein G is C or N; R₁ is NH₂, alkyl, substituted alkyl, alkenyl,substituted alkenyl, aralkyl, amino, alkylamino, aralkylamino,substituted alkylamino, heterocycloalkyl, heterocycloalkylamino,aminoalkylamino, hetrocycloalkylamino, polyalkylamino, or an RNAcleaving moiety; R₂ is alkyl, substituted alkyl, alkenyl, substitutedalkenyl, aralkyl, amino, alkylamino, aralkylamino, substitutedalkylamino, heterocycloalkyl, heterocycloalkylamino, aminoalkylamino,hetrocycloalkylamino, polyalkylamino, or an RNA cleaving moiety; and Yis H, a nitrogen protecting group, or a sugar moiety.

In certain preferred embodiments, Y is ribose. In a more preferredembodiment, Y is deoxyribose. In another preferred embodiment, Y is asugar analog, preferably the deoxyribose type.

In certain preferred embodiments, R₁ is alkyl having up to about 12carbon atoms. In another preferred embodiment, R₁ is alkenyl having upto about 12 carbon atoms. In still another preferred embodiment, R₁ isaralkyl having from about 6 to about 30 carbon atoms.

In other preferred embodiments, Y is ribose or deoxyribose and R₁ isalkyl having up to about 12 carbon atoms. In another preferredembodiment, Y is ribose or deoxyribose and R₁ is alkenyl having up toabout 12 carbon atoms. In yet another preferred embodiment, Y is riboseor deoxyribose and R₁ is aralkyl having from about 6 to about 30 carbonatoms.

In certain other preferred embodiments, G is N, R₁ is alkyl, R₂ isamino, and Y is ribose or deoxyribose. In another preferred embodiment,G is N, R₁ is alkenyl, R₂ is amino, and Y is ribose or deoxyribose. Inother preferred embodiments, G is N, R₁ is aralkyl, R₂ is amino, and Yis ribose or deoxyribose. In other preferred embodiments, G is N; R₁ is1-methyloctane, 1-propene, phenylmethyl, or napthylethyl; R₂ is amino;and Y is ribose or deoxyribose.

In certain preferred embodiments, the RNA cleaving moiety comprises aportion reactive with said RNA. In another preferred embodiment, the RNAcleaving moiety further comprises a tether portion for attaching thereactive portion to the balance of the composition.

Numerous amine protecting groups are known in the art, and can be used,including the allyloxycarbonyl (Alloc), benzyloxycarbonyl (CBz),chlorobenzyloxycarbonyl, t-butyloxycarbonyl (Boc),fluorenylmethoxycarbonyl (Fmoc), isonicotinyloxycarbonyl (i-Noc) groups.(see, e.g., Veber and Hirschmann, et al., J. Org. Chem. 1977, 42, 3286and Atherton, et al., The Peptides, Gross and Meienhofer, Eds, AcademicPress; New York, 1983; Vol. 9 pp. 1-38). For example, it is known thatthe Boc group can protect an amine group from base and from reducingconditions but that it can be removed with acid.

The invention further provides compositions comprising a sugar and basemoiety as discussed above, with the 3' position of the sugar moietyderivatized with an activated phosphate group.

In another aspect of this invention, mixed sequence oligonucleotidesincorporating at least one compound as set forth above are presented.

In another aspect of the invention, the compounds have the formula:##STR2## wherein G is C or N; R₃ is H, NH₂, alkyl, substituted alkyl,alkenyl, substituted alkenyl, aralkyl, amino, alkylamino, aralkylamino,substituted alkylamino, heterocycloalkyl, heterocycloalkylamino,aminoalkylamino, hetrocycloalkylamino, polyalkylamino, or an RNAcleaving moiety; R₄ is NH₂, alkyl, substituted alkyl, alkenyl,substituted alkenyl, aralkyl, amino, alkylamino, aralkylamino,substituted alkylamino, heterocycloalkyl, heterocycloalkylamino,aminoalkylamino, hetrocycloalkylamino, polyalkylamino, or an RNAcleaving moiety; and Y is H, a nitrogen protecting group, or a sugarmoiety; provided that when R₃ is H, R₄ is not NH₂.

In certain preferred embodiments, Y is ribose. In a more preferredembodiment, Y is deoxyribose. In another preferred embodiment, Y is asugar analog, preferably the deoxyribose type.

In certain preferred embodiments, R₃ is alkyl having up to about 12carbon atoms. In another preferred embodiment, R₃ is alkenyl having upto about 12 carbon atoms. In still another preferred embodiment, R₃ isaralkyl having from about 6 to about 30 carbon atoms.

In other preferred embodiments, Y is ribose or deoxyribose and R₃ isalkyl having up to about 12 carbon atoms. In another preferredembodiment, Y is ribose or deoxyribose and R₃ is alkenyl having up toabout 12 carbon atoms. In yet another preferred embodiment, Y is riboseor deoxyribose and R₃ is aralkyl having from about 6 to about 30 carbonatoms.

In certain other preferred embodiments, G is N, R₃ is alkyl, R₄ is NH₂,and Y is ribose or deoxyribose. In another preferred embodiment, G is N,R₃ is alkenyl, R₄ is NH₂, and Y is ribose or deoxyribose. In otherpreferred embodiments, G is N, R₃ is aralkyl, R₄ is NH₂, and Y is riboseor deoxyribose.

In certain preferred embodiments, the RNA cleaving moiety comprises aportion reactive with said RNA. In another preferred embodiment, the RNAcleaving moiety further comprises a tether portion for attaching thereactive portion to the balance of the composition.

Numerous amine protecting groups are known in the art, and can be used,including the allyloxycarbonyl (Alloc), benzyloxycarbonyl (CBz),chlorobenzyloxycarbonyl, t-butyloxycarbonyl (Boc),fluorenylmethoxycarbonyl (Fmoc), isonicotinyloxycarbonyl (i-Noc) groups.(see, e.g., Veber and Hirschmann, et al., J. Org. Chem. 1977, 42, 3286and Atherton, et al., The Peptides, Gross and Meienhofer, Eds, AcademicPress; New York, 1983; Vol. 9 pp. 1-38). For example, it is known thatthe Boc group can protect an amine group from base and from reducingconditions but that it can be removed with acid.

The invention further provides compositions comprising a sugar and basemoiety as discussed above, with the 3' position of the sugar moietyderivatized with an activated phosphate group.

In another aspect of this invention, mixed sequence oligonucleotidesincorporating at least one compound as set forth above are presented.

In another aspect of the invention, novel methods for synthesizing thecompounds of the invention are provided. The synthesis of the3-deazaguanine ring system has been most widely achieved via thebase-catalyzed cyclization of a5(4)-cyanomethyl-imidazole-4(5)-carboxamide. Cook, et al., J. Am. Chem.Soc. 1975, 97, 2916; Cook, et al., R. K. T. Med. Chem. 1978, 21, 1212,the disclosures of which are incorporated herein by reference in theirentirety. Both the 2'-deoxy- and the 3-deazaguanosines have also beensynthesized using a synthetic scheme that relies on this novelcyclization.

Generally, the compounds of the invention may be synthesized byemploying a mild alkylation on the methylene carbon of an imidazoleprecursor to the 3-deazapurine ring system. The starting material may bea 5-cyano-methyl-imidazole carboxylate, which can be synthesizedaccording to a known procedure. Journal of Medicinal Chemistry, Vol. 27p. 1389 (1984). For nucleoside synthesis, a sugar moiety is attached tothe 1-position of the imidazole ring of the starting material before thealkylation step. Methods of attaching a sugar moity to the imidazolering are well known to those skilled in the art.

For base synthesis, the ester functionality of the starting material, 5cyanoimidazole carboxylate, is protected with an ester protecting groupbefore the alkylation step. Any ester protecting groups and methods ofattaching ester protecting groups known in the art may be used.

Generally, reactive functionalities emanating from the 3-position of the3-deazapurine ring can be obtained by a multi-step synthesis under thefollowing reaction conditions. The methylene moiety of the staringmaterial is alkylated with halogenated reactive functionalities, such asan alkyl, alkenyl, or aryl halide.

The alkylated carboxylates are converted to the correspondingcarboxamides by ammonolysis at elevated temperature. The alkylatedcarboxamides are subsequently cyclized using one of several availableprocedures. Cook, et al., J. Am. Chem. Soc. 1975, 97, 2916; Cook, etal., R. K. J. Med. Chem. 1978, 21, 1212. For example, cyclized productscan be obtained using a two-step procedure employing liquid andmethanolic ammonia. The protecting groups are removed from the imidazoleintermediate with hydrochloric acid.

The corresponding nucleotides of the invention can be prepared byprotecting the 5' position of the sugar moiety of a nucleosidic unit andderivatizing the 3' position with an appropriate phosphoramidite orother activated phosphate. These are inserted into oligonucleotides as5'-DMT-3'-cyanoethyl phosphoramidites through routine solid statesynthetic techniques.

Oligonucleotide or oligonucleotide analogs incorporating at least one ofthe novel compounds of the invention may be synthesized and are withinthe ambit of this invention. Oligonucleotides or oligonucleotide analogsincorporating the novel compounds of the invention may be synthesized,conveniently through solid state synthesis of known methodology, to becomplementary to or at least to be specifically hybridizable with thepreselected nucleotide sequence of the RNA or DNA. Nucleic acidsynthesizers are commercially available and their use is generallyunderstood by persons of ordinary skill in the art as being effective ingenerating nearly any oligonucleotide of reasonable length which may bedesired. See, e.g., Caruthers, Oligonucleotides, Antisense Inhibitors ofGene Expression., pp. 7-24, J. S. Cohen, ed. (CRC Press, Inc. BocaRaton, Fla., 1989); J. Am. Chem. Society, 1990, 112, 1253-1255; Beaucageet al., Tetrahedron Letters, 1981, 22, 1859-1862.

The sugar moiety of the nucleosidic units incorporated onto theoligonucleotide compositions is preferably the deoxyribose type. Thegroups linking the bases together may be the usual sugar phosphatenucleic acid backbone, but may also be modified as a phosphorothioate,methylphosphonate, or phosphate alkylated moiety to further enhance thesugar modified oligonucleotide properties, along with removal of a5'-methylene group and/or carbocyclic sugar. Sugar modifications aredisclosed as set forth in PCT Application Number PCT\US91\00243 assignedto a common assignee hereof, entitled "Compositions and Methods forDetecting and Modulating RNA Activity and Gene Expression,"International Publication Number WO 91/10671, the disclosures of whichare incorporated herein by reference in order to disclose more fullysuch modifications.

DETAILED DESCRIPTION OF THE INVENTION

This invention presents novel heterocyclic compounds based on the3-deazapurine core that may be used intermediates for oligonucleotidecompositions. In particular, this invention provides nucleosides,nucleoside analogs, nucleotides, nucleotide analogs, heterocyclic bases,and heterocyclic base analogs. The compounds of the invention possessunique steric properties that result in modified biological activity andbetter cellular transport properties. These attributes make thesecompositions useful intermediates for oligonucleotide compositions.

The compounds of the invention may have at least one RNA cleaving moietyor other moiety capable of interacting with an RNA appended thereto,which are adapted for placement of the reactive RNA cleaving moiety orother reactive moiety into the minor groove site of the hybrid structureformed from the RNA and the composition through careful selection of thesites of attachment of the RNA cleaving moieties. Incorporation of thesenovel compounds into oligonucleotides compositions improves thesecompositions' pharmacokinetic and pharmacodynamic properties, thecompositions' resistance to nucleases, improves the compositions'binding capabilities without any concomitant interference with theWatson-Crick binding, and enhances the compositions' penetration intocells.

The functionalized sites on the base units, which in turn may beincorporated into modified oligonucleotides, is critical in the designof compositions for sequence-specific destruction or modulation oftargeted RNA. The functionality must not interfere with Watson-Crickbase pair hydrogen bonding rules as this is the sequence-specificrecognition/binding factor essential for selection of the desired RNA tobe disrupted.

It has now been found that certain positions on the nucleosides ofdouble stranded nucleic acids are exposed in the minor groove and may besubstituted without affecting Watson-Crick base-pairing or duplexstability. Reactive or non-reactive functionalities placed in thesepositions in accordance with this invention can best initiate cleavageand destruction of targeted RNA or interfere with its activity. Thesites of functionality in the heterocyclic compounds of the inventionare novel, and have been preferably designed such that thefunctionalities will reside in or on the minor groove formed by theheteroduplex between modified oligonucleotides and targeted RNA.

The present invention also provides novel methods for the synthesis ofthe compounds of the invention employing a mild alkylation procedure onan imidazole precursor to the 3-deazapurine ring system.

The compounds possessing the required functionality in the heterocyclicbase portion may be used to prepare desired oligonucleotides andoligonucleotide analogs. These oligonucleotide and oligonucleotideanalogs are also within the ambit of this invention. Oligonucleotidesand oligonucleotide analogs incorporating the novel compounds of theinvention are believed to increase the oligonucleotide compositions'nuclease resistance, and thus, facilitate anti-sense therapeutic,diagnostic use, or research reagent use of these antisense agents.

In the context of this invention, a "nucleoside" is a nitrogenousheterocyclic base linked to a pentose equivalent, either a ribose, deoxyribose, or derivative or analog thereof. The term "nucleotide" means aphosphoric acid ester of a nucleoside comprising a nitrogenousheterocyclic base, a pentose equivalent, and one or more phosphate orother backbone forming groups; it is the monomeric unit of anoligonucleotide. The term "oligonucleotide" refers to a plurality ofjoined nucleotide units formed in a specific sequence from naturallyoccurring heterocyclic bases and pentofuranosyl equivalent groups joinedthrough phosphodiester or other backbone forming groups. Nucleotideunits may be nucleic acid bases such as guanine, adenine, cytosine,thymine, or derivatives thereof. The pentose equivalent may bedeoxyribose, ribose, or groups that substitute therefore. This termrefers to both naturally occurring and synthetic species formed orderived from naturally occurring subunits. The terms "antisense agents"and "oligonucleotide compositions" as used in the context of thisinvention encompass oligonucleotides and oligonucleotide analogs. In thecontext of this invention, "activated phosphate group" meansphosphorothioates, methyl phosphonates, phosphoramidites, andphosphorotriesters (phosphate methylated DNA) and any other groups knownto those skilled in the art.

"Modified base," "base analog," "modified nucleoside," "nucleotideanalog," or "modified nucleotide," in the context of this inventionrefer to moieties that function similarly to their naturally occurringcounterparts but have been functionalized to change their properties.

"Sugar moiety" as used in the context of this invention refers tonaturally occurring sugars, such as ribose or deoxyribose, and sugarsand non-sugar analogs that have been functionalized to change theirproperties.

"Oligonucleotide analogs" or "modified oligonucleotides" as used inconnection with this invention, refer to compositions that functionsimilarly to natural oligonucleotides but that have non-naturallyoccurring portions. Oligonucleotide analogs or modified oligonucleotidesmay have altered sugar moieties, altered bases, both altered sugars andbases or altered inter-sugar linkages, for example phosphorothioates andother sulfur containing species which are known for use in the art.

In the context of the invention, "improved pharmacodynamic property"means improved oligonucleotide uptake, enhanced oligonucleotideresistance to degradation, and/or strengthened sequence-specifichybridization with RNA. "Improved pharmacokinetic property" meansimproved oligonucleotide uptake, distribution, metabolism or excretion.

In one aspect of the invention, the compounds have the formula: ##STR3##wherein G is C or N; R₁ is NH₂, alkyl, substituted alkyl, alkenyl,substituted alkenyl, aralkyl, amino, alkylamino, aralkylamino,substituted alkylamino, heterocycloalkyl, heterocycloalkylamino,aminoalkylamino, hetrocycloalkylamino, polyalkylamino, or an RNAcleaving moiety; R₂ is alkyl, substituted alkyl, alkenyl, substitutedalkenyl, aralkyl, amino, alkylamino, aralkylamino, substitutedalkylamino, heterocycloalkyl, heterocycloalkylamino, aminoalkylamino,hetrocycloalkylamino, polyalkylamino, or an RNA cleaving moiety; and Yis H, a nitrogen protecting group, or a sugar moiety.

In certain preferred embodiments, Y is ribose or deoxyribose. In a morepreferred embodiment, Y is deoxyribose. In another preferred embodiment,Y is a sugar analog, preferably the deoxyribose type. Sugar analogs withsubstituents at the 3' or 5' of deoxyribose, or at the 2', 3', or 5' ofribose are contemplated. Suitable substituents on the sugar moietyinclude, but are not limited to, O, H, lower alkyl, substituted loweralkyl, aralkyl, heteroaralkyl, heterocycloalkyl, amino-alkylamino,heterocycloalkyl, polyalkylamino, substituted silyl, F, Cl, Br, CN, CF₃,OCF₃, OCN, O-alkyl, S-alkyl, SOMe, SO₂ Me, ONO₂, NO₂, N₃, NH₂, NH-alkyl,OCH₂ CH═CH₂, OCH═CH₂, OCH₂ CCH, OCCH, or an RNA cleaving moiety.

Generally, substituted sugars may be synthesized according to themethods disclosed in PCT Patent Application Number PCT\US91\00243assigned to a common assignee hereof, entitled "Compositions and Methodsfor Detecting and Modulating RNA Activity and Gene Expression," thedisclosures of which are incorporated herein by reference to disclosemore fully such modifications.

For example, a substituted sugar as, methyl3-O-(t-butyldiphenylsilyl)-2,5-dideoxy-5-C-formyl-α/β-D-erythro-pentofuranoside,can be prepared by modifying 2-deoxy-D-ribose to methyl2-deoxy-α/β-D-erythro-pentofuranoside (prepared according to the methodof M.S. Motawai and E.B. Pedersen, Liebigs Ann. Chem. 1990, 599-602),which on selective tosylation followed by 3-O-silylation gave methyl3-O-(t-butyldimethylsilyl)-2-deoxy-5-O-tosyl-α/β-D-erythro-pentofuranoside.

In certain other preferred embodiments, R₁ is alkyl having up to about12 carbon atoms. In another preferred embodiment, R₁ is alkenyl havingup to about 12 carbon atoms. In still another preferred embodiment, R₁is aralkyl having from about 6 to about 30 carbon atoms. In anotherpreferred embodiment, R₁ is 1-methyloctane. In a more preferredembodiment, R₁ is 1-propene. In still a more preferred embodiment, R₁ isphenylmethyl. In yet a more preferred embodiment, R₁ is napthylethyl.

In other preferred embodiments, Y is ribose or deoxyribose and R₁ isalkyl having up to about 12 carbon atoms. In another preferredembodiment, Y is ribose or deoxyribose and R₁ is alkenyl having up toabout 12 carbon atoms. In yet another preferred embodiment, Y is riboseor deoxyribose and R₁ is aralkyl having from about 6 to about 30 carbonatoms.

In certain other preferred embodiments, G is N, R₁ is alkyl, R₂ isamino, and Y is ribose or deoxyribose. In another preferred embodiment,G is N, R₁ is alkenyl, R₂ is amino, and Y is ribose or deoxyribose. Inother preferred embodiments, G is N, R₁ is aralkyl, R₂ is amino, and Yis ribose or deoxyribose. In other preferred embodiments, G is N; R₁ is1-methyloctane, 1-propene, phenylmethyl, or napthylethyl; R₂ is amino;and Y is ribose or deoxyribose.

R₁ and/or R₂ may be any of the following alkyl, alkenyl, aryl, amino, orcyclic groups. Alkyl groups of the invention include, but are notlimited to, C₁ -C₁₂ straight and branched chained alkyls such as methyl,ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl,undecyl, dodecyl, isopropyl, 2-butyl, isobutyl, 2-methylbutyl,isopentyl, 2-methyl-pentyl, 3-methylpentyl, 2-ethylhexyl,2-propylpentyl. Alkenyl groups include but are not limited tounsaturated moieties derived from the above alkyl groups including butnot limited to vinyl, allyl, crotyl, propargyl. Aryl groups include butare not limited to phenyl, tolyl, benzyl, naphthyl, anthracly,phenanthryl, and xylyl. Suitable heterocyclic groups include but are notlimited to imidazole, tetrazole, triazole, pyrrolidine, piperidine,piperazine and morpholine. Amines include amines of all of the abovealkyl, alkenyl and aryl groups including primary and secondary aminesand "masked amines" such as phthalimide. Amines are also meant toinclude polyalkylamino compounds and aminoalkylamines such asaminopropylamine and further heterocycloalkylamines such as imidazol-1,2 or 4-yl-propylamine. Substituent groups for the above include but arenot limited to other alkyl, haloalkyl, alkenyl, alkoxy, thioalkoxy,haloalkoxy and aryl groups as well as halogen, hydroxyl, amino, azido,carboxy, cyano, nitro, mercapto, sulfides, sulfones and sulfoxides.Other suitable substituent groups also include rhodamines, coumarins,acridones, pyrenes, stilbenes, oxazolopryidocarbazoles, anthraquinones,phenanthridines, phenazines, azidobenzenes, psoralens, porphyrins andcholesterols. Pendant groups that do not possess reactive functionality,do not initiate chemical reactions, but enhance the oligonucleotidecompositions' pharmacodynamic and pharmacokinetic properties may also beused without departing from the spirit of the invention. Such groupsinclude, but are not limited to, alkyl chains, polyamines, ethyleneglycols, polyamides, aminoalkyl chains, amphipathic moieties, points forreporter group attachment, and intercalators attached to any of thepreferred sites for attachment.

In other preferred embodiments, the RNA cleaving moiety comprises aportion reactive with said RNA. It is believed desirable in accordancewith certain preferred embodiments, to attach the RNA cleaving portionto one of the nucleosides forming the subunits of the oligonucleotidecompositions' targeting portion.

In another preferred embodiment, the RNA cleaving moiety furthercomprises a tether portion for attaching the reactive portion to thebalance of the composition. It is not necessary to tether more than one,or perhaps two RNA cleaving functionalities to oligonucleotidecompositions in accordance with this invention in order to provide thebenefits of the invention. Thus, an RNA cleaving moiety will preferablybe tethered to a relatively small proportion of the subunits, generallyonly one or two, comprising the oligonucleotide compositions, which isthe targeting portion of the compositions of the invention. In otherembodiments, of the invention, however, all of the nucleotides in anoligonucleotide can be modified to include one or more RNA cleavingmoiety groups.

The half life of the perfectly formed duplex will be greatly effected bythe positioning of the tethered functional group. Inappropriatepositioning of functional groups, such as placement on the Watson/Crickbase pair sites, would preclude duplex formation. Other attachment sitesmay allow sequence-specific binding but may be of such low stabilitythat the reactive functionality will not have sufficient time toinitiate RNA disruption.

It is believed that attaching RNA cleaving moieties in accordance withthe foregoing considerations will permit those moieties to lie in theminor groove of the hybrid formed from the composition of the presentinvention and the messenger RNA for which modulation is desired. It ispossible that other positions for attachment of the RNA cleavingmoieties having a similar effect may be found, especially when furthermodifications of the purine structure is undertaken as may be done bypersons of ordinary skill in the art without deviating from the spiritof the present invention. Once again, it is to be understood thatpreferably one, or at most a few RNA cleaving moieties are generally tobe employed. Thus, artisans in the field will have great latitude inselecting means of attachment of the RNA cleaving moieties, thepharmacodynamic improving group or the pharmacokinetic improving groupin accordance with this invention.

The RNA cleaving moieties of the compositions of the present inventionare designed in such a fashion that they can be effective in performingtheir proximate task, leading to the desired modulation of RNA activity.RNA cleaving moieties may include heteroatomic substitutions; theseheteroatomic substituents include, but are not limited to, amides andpolyamides, and heterocyclics, especially imidazoles and other nitrogenheterocycles.

Generally, protecting groups are known per se as chemical functionalgroups that can be selectively appended to and removed fromfunctionalities, such as amine groups. These groups are present in achemical compound to render such functionality inert to chemicalreaction conditions to which the compound is exposed. See, e.g., Greeneand Wuts, Protective Groups in Organic Synthesis, 2d edition, John Wiley& Sons, New York, 1991. Numerous amine protecting groups are known inthe art, including, but not limited to, the allyloxycarbonyl (Alloc),benzyloxycarbonyl (CBz), chlorobenzyloxycarbonyl, t-butyloxycarbonyl(Boc), fluorenylmethoxycarbonyl (Fmoc), isonicotinyloxycarbonyl (i-Noc)groups. (see, e.g., Veber and Hirschmann, et al., J. Org. Chem. 1977,42, 3286 and Atherton, et al., The Peptides, Gross and Meienhofer, Eds,Academic Press; New York, 1983; Vol. 9 pp. 1-38). For example, it isknown that the Boc group can protect an amine group from base and fromreducing conditions but that it can be removed with acid. Other nitrogenprotecting groups will be apparent to those skilled in the art and maybe used without detracting from the spirit of the invention.

Another aspect of the invention presents compounds having the formula:##STR4## wherein G is C or N; R₃ is H, NH₂, alkyl, substituted alkyl,alkenyl, substituted alkenyl, aralkyl, amino, alkylamino, aralkylamino,substituted alkylamino, heterocycloalkyl, heterocycloalkylamino,aminoalkylamino, hetrocycloalkylamino, polyalkylamino, or an RNAcleaving moiety; R₄ is NH₂, alkyl, substituted alkyl, alkenyl,substituted alkenyl, aralkyl, amino, amino alkylamino, aralkylamino,substituted alkylamino, heterocycloalkyl, heterocycloalkylamino,aminoalkylamino, hetrocycloalkylamino, polyalkylamino, or an RNAcleaving moiety; and Y is H, a nitrogen protecting group, or a sugarmoiety; provided that when R₃ is H, R₄ is not NH₂.

In certain preferred embodiments, Y is ribose or deoxyribose. In a morepreferred embodiment, Y is deoxyribose. In another preferred embodiment,Y is a sugar analog, preferably the deoxyribose type. Sugar analogs withsubstituents at the 3' or 5' of deoxyribose, or at the 2', 3', or 5' ofribose are contemplated. Suitable substituents on the sugar moietyinclude, but are not limited to, O, H, lower alkyl, substituted loweralkyl, aralkyl, heteroaralkyl, heterocycloalkyl, amino-alkylamino,heterocycloalkyl, polyalkylamino, substituted silyl, F, Cl, Br, CN, CF₃,OCF₃, OCN, O-alkyl, S-alkyl, SOMe, SO₂ Me, ONO₂, NO₂, N₃, NH₂, NH-alkyl,OCH₂ CH═CH₂, OCH═CH₂, OCH₂ CCH, OCCH, or an RNA cleaving moiety. Thediscussion of sugar moieties set forth above in connection with theother compounds of the invention is fully applicable here.

In certain preferred embodiments, R₃ is alkyl having up to about 12carbon atoms. In another preferred embodiment, R₃ is alkenyl having upto about 12 carbon atoms. In still another preferred embodiment, R₁ isaralkyl having from about 6 to about 30 carbon atoms. In a morepreferred embodiment, R₃ is 1-methyloctane. In a more preferredembodiment, R₃ is 1-propene. In still a more preferred embodiment, R₃ isphenylmethyl. In yet a more preferred embodiment, R₃ is napthylethyl.

In other preferred embodiments, Y is ribose or deoxyribose and R₃ isalkyl having up to about 12 carbon atoms. In another preferredembodiment, Y is ribose or deoxyribose and R₃ is alkenyl having up toabout 12 carbon atoms. In yet another preferred embodiment, Y is riboseor deoxyribose and R₃ is aralkyl having from about 6 to about 30 carbonatoms.

In certain other preferred embodiments, G is N, R₃ is alkyl, R₄ is NH₂,and Y is ribose or deoxyribose. In another preferred embodiment, G is N,R₃ is alkenyl, R₄ is NH₂, and Y is ribose or deoxyribose. In otherpreferred embodiments, G is N, R₃ is aralkyl, R₄ is NH₂, and Y is riboseor deoxyribose. In other preferred embodiments, G is N; R₃ is1-methyloctane, 1-propene, phenylmethyl, or napthylethyl; R₄ is amino;and Y is ribose or deoxyribose.

R₃ and R₄ may be any of the alkyl, alkenyl, aryl, amino, or cyclicgroups as set forth above.

In other preferred embodiments, the RNA cleaving moiety and nitrogenprotecting groups may be as set forth above in connection with thepreviously discussed compounds. The discussion set forth above is fullyapplicable here.

Generally, the bases of the invention may be synthesized by startingwith a 5-cyanomethyl imidazole carboxylate, protecting the ester with anester protecting group, treating the compound with sodium hydride,followed by electrophilic substitution with an alkyl, alkenyl, or arylhalide, preferably bromine. The carboxylates are converted to thecorresponding carboxamides by treatment with methanolic ammonia atelevated temperature. The alkylated products are subsequently cyclized.Cook, et al., J. Am. Chem. Soc. 1975, 97, 2916; Cook, et al., R. K. J.Med. Chem. 1978, 21, 1212; Revankar, supra.

The following discussion provides an illustrative example of a possiblesynthetic route. The bases of the invention may be synthesized byprotecting the methyl 5(4)-cyanomethyl-imidazole-4(5)-carboxylate'simidazole ring nitrogens with a protecting group such as atetrahydropyranyl group. A reaction with 2,3-dihydropyran in thepresence of tosic acid yields the 5 and 7 tetrahydro-pyranyl positionalisomers of 4-cyanomethyl-imidazole-5-carboxylates in roughly a 2:1ratio. These isomers are separated in order to isolate the isomer with atetrahydropyranyl protecting group in a position removed from theproposed site of alkylation. Cook et al., J. Med. Chem., 1978, 21, 1212.

The 7 tetrahydropyranyl positional isomer is then alkylated by adding adilute solution of the alkylating electrophile in acetonitrile to thereaction mixture, the reaction mixture is stirred under an inertatmosphere for periods of 3-18 hours. The reaction media and productsare isolated by flash-column chromatography using silica gel. In eachcase, the products are approximately 1:1 mixtures of isomers, asdetermined by an integration of the signals for the H-2 protons in the ¹H-NMR. The alkylated product mixtures were subsequently treated withmethanolic ammonia and heated at 75° C. in a sealed vessel to yield thecyclized products. When the ammonolysis was conducted at 100° C., therewas extensive decomposition and no products could be isolated. Themixtures were evaporated under reduced pressure to afford light coloredsolids which decomposed rapidly when exposed to air and moisture. Thecrude reaction products were thoroughly rid of all ammonia and treatedwith 1N HCl in methanol for several hours to remove thetetrahydropyranyl protecting groups, which yielded the 7-alkyl(aryl)-6-amino-1,5-dihydroimidazo 4,5-c!pyridin-4-one products as stablehydrochloride salts. Hartman, et al., J. Labelled Compd. Radiopharm.,1985, 23, 35. The hydrochloride salts gave satisfactory C,H,N analysesand ¹ H-NMR spectra after months of storage, attesting to theirlong-term stability. The following reaction scheme illustrates thissynthesis. ##STR5##

Compounds of the invention having a sugar moiety at the 1-position ofthe imidazole ring invention may be synthesized using a proceduresimilar to that used for the previously discussed bases of theinvention. Generally, reactive functionalities emanating from the3-position of a 2'-deoxy-3-deazapurine can be obtained by a multi-stepsynthesis starting with the alkylation of the methylene moiety of acyanomethyl imidazole derivative with various electrophiles, such ashalogenated reactive functionalities. The alkylated product isammonylated to yield the carboxamide. The carboxamide ofmethyl-5-(cyanomethyl)-1-(2'deoxy-3,5-di-O-p-toluyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate may be obtained from the ammonolysis of themethyl 5-cyanomethyl-imidazole-4-carboxylates, and5-cynanomethyl-1-(2-deoxy-3,5-di-O-p-toluoylp-β-D-erythro-pentofuranosyl)-imidazole-4-carboxylate.Cyclized products may be obtained using a two-step procedure employingliquid and then methanolic ammonia. The alkylated imidazoles are treatedwith methanolic ammonia to remove the toluoyl groups from the sugarmoiety. These may be inserted into oligonucleotides as5'-DMT-3'-cyanoethyl phosphoramidites through routine solid statesynthetic techniques.

The starting imidazole material, 5-cyano(substituted)-methyl-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate, for the above discussed reaction, can besynthesized according to a known procedure. Journal of MedicinalChemistry, Vol. 27 p. 1389 (1984). The synthetic intermediatemethyl-5-(cyanomethyl)-1-(2'deoxy-3,5-di-O-p-toluyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate was obtained from the sodium salt glycosylationof methyl 5(4)-cyanomethyl-imidazole-4(5)carboxylate with1-chloro-2-deoxy-3,5-di-O-p-toluoyl-a-D-erythro-pentofuranose(chlorosugar) in acetonitrile. Positional isomers corresponding tomethyl5-cynanomethyl-1-(2-deoxy-3,5-di-O-p-toluoylp-β-D-erythro-pentofuranosyl)-imidazole-4-carboxylateand methyl4-cyanomethyl-1-(2-deoxy-3,5-di-O-p-toluoyl-b-D-erythro-pentofuranosyl)-imidazole5-carboxylate were obtained in 1:1.5 ratios and in good overall yields.The most favorable ratio of positional isomers was obtained when thechloro-sugar used in the condensation was free of acidic contaminantsand anhydrous conditions were maintained during the course of thereaction. Revankar, supra. Other synthetic methods will be apparent tothose skilled in the art.

The nucleosides may be synthesized under the following reactionconditions. The5-cynanomethyl-1-(2-deoxy-3,5-di-O-p-toluoylp-β-D-erythro-pentofuranosyl)-imidazole-4-carboxylatewas equilibrated with an excess of sodium hydride at room temperature inacetonitrile. A dilute solution of the alkylating agent in acetonitrilewas introduced into the reaction mixture and the reaction mixturestirred under an inert atmosphere for a period of 3-18 hours. Thereaction media and products are then isolated by flash-columnchromatography. This procedure yields mixtures of diastereomericproducts. For example, in the case of the ethyl 5-(benzyl cyano!methyl)imidazole-4-carboxylate or the methyl 5-(cyano2-(1-naphthyl)ethyl!methyl)imidazole-4-carboxylate 2'-deoxynucleosides,these mixtures were resolved according to the procedures specified inCook, J. Med. Chem., supra.

For example, in the case of the methyl 5-(benzylcyano!methyl)imidazole-4-carboxylate or the methyl 5-(cyano2-(1-naphthyl)ethyl!methyl)imidazole-4-carboxylate 2'-deoxynucleosides,these mixtures were resolved and the diastereomers characterizedindividually by ¹ H-NMR. In these cases, each isomer exhibited a metheneproton resonance as a doublet of doublets at δ,4.8 to 5.5 ppm,indicative of a tertiary proton, Pretsch, supra, as part of an AM₂system. In addition, these compounds exhibited nitrile absorption bandsat 2220 to 2240 cm⁻¹ in their infrared spectra.

The alkylation products, methyl 5-(cyanoalkyl!methyl)-1-(2-deoxy-3,5di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate nucleosides are heated in liquid ammonia at 90°C. for 18-20 hours in a stainless steel bomb to yield the correspondingdeprotected carboxamides. Further heating of the carboxamides withmethanolic ammonia at 95° C. yields the desired nucleoside products,2'-deoxy-3-alkyl(aryl)-3-deazapurines. This two step procedure resultedin better yields of the cyclized products than obtained by prolongedheating of the methyl 5-cyanomethyl-imidazole-4-carboxylates in liquidammonia. Cook, J. Am. Chem. Society, supra. The following reactionscheme illustrates the synthesis of the nucleosides of the invention.##STR6##

The electrophiles suitable for practicing the invention include, but arenot limited to, alkyl, alkenyl, aryl, amino, cyclic, or heterocycliccompounds having a group. The suitable leaving groups include, but arenot limited to, chloride, flouride, iodine, and bromine, with brominepreferred.

Any ester protecting groups known to those skilled in the art may beused; tetrahydropyranyl is an example of such a group. However, variousester protecting groups are known and may be used without detractingfrom the spirit of the invention. See Green and Wuts, spura.

Methods of synthesizing compounds where the 3 position of the imidazolering system is carbon rather than nitrogen will be apparent to thoseskilled in the art and may be used without detracting from the spirit ofthe invention. See Revankar, supra.

Methods of attaching sugar moieties to the imidazole ring are well knownin the art. See Revankar, supra.

In preparing certain of the compounds of the invention fugitive maskinggroups may be used. Such masking groups allow for ease of synthesis ofthe compounds. The masking groups are subsequently converted to thedesired functionality. Such conversion preferably occurs during astandard deblocking step for a later reaction. As an example of use ofthis procedure is the use of phthalimide group for the introduction ofan amino functionality. Alkyl phthalimides are attached at the properposition in a compound of interest, as for example a nucleoside, via asuitable intermediate such as an N-(haloalkyl)phthalimide. Uponcompletion of the synthesis of the compound of interest it is then usedas a structural nucleotide for oligonucleotide synthesis utilizingstandard oligonucleotide synthetic techniques on a nucleotidesynthesizer. After the desired oligonucleotide or oligonucleotide analogis completed, it is cleaved from the synthesizer support and in doing sothe cleaving reagent also converts the alkylphthalimide to the desiredalkylamine. The above procedure can be expanded to attach longer chainpolyamino functionalities to the oligonucleotides or oligonucleotideanalogs of the invention. Nucleotides, nucleotide analogs,oligonucleotide analogs, or oligonucleotides having a first alkylaminofunctionality are treated with a further N-(haloalkyl) phthalimide. Theextended functionality is then treated to yield the terminal aminegroup. This can be repeated to further extend the polyaminofunctionality as desired. Alternately, the extended polyaminofunctionality is first synthesized and reacted with the first alkylaminofunctionality to form the polyamino functionality.

If any of the reactions yield a reaction slurry from which the productmust be recovered this can be done according to nay methods known in theart. Methods of recovering the sample include any filtration orseparation techniques known in the art. Such methods include, but arenot limited to, vacuum filtration, separatory extraction, ordistillation. A preferred method is filtration using air or liquid, butother methods will be apparent to those skilled in the art.

If any products require further washing with organic solvents toseparate impurities, reaction intermediates, or byproducts can be doneaccording to methods known in the art. Suitable organic solventsinclude, but are not limited to, ether, methanol, ethanol, ethylacetate, or hexanes. Other types of solvents will be apparent to thoseskilled in the art. Any organic solvent should be evaporated usingmethods known in the art. Evaporation methods may be accomplished atroom temperature, by vacuum, aspiration, or by using latent heat. Theevaporation methods are not limited to these techniques and othertechniques will be apparent to those skilled in the art.

The reaction product may require purification. This may be accomplishedusing purification techniques known in the art. These techniquesinclude, but are not limited to, column chromatography, flashchromatography, recrystillization, or gel chromatography. Flashchromatography on silica gel is preferred but other methods will beapparent to those skilled in the art. Any organic solvents suitable forchromatography may be used. These include, but are not limited to,methanol, acetonitrile, hexanes, carbontrichloride, and ethyl acetate.Other solvents will be apparent to those skilled in the art and may beused without detracting from the spirit of the invention.

Generally, nucleotides of the invention may be prepared by protectingthe 5' position of the sugar moiety of the imidazole ring andderivatizing the 3' position with an appropriate phosphoramidite orother activated phosphate suitable for use on a DNA synthesizer.

Alkylation of the imidazole active methylene with α-halo-α- reactivefunctionality! acetaldehyde dimethylketal or α-halo-methyl- reactivefunctionality! ketone with subsequent amination provides imidazolecarboxamides. These can be converted to5'-DMT-3'-cyanoethylphosphoramidites and inserted into sequence specificoligonucleotides. The prepared oligonucleotides, which are in blockedform, are removed from the solid support upon which they are elaboratedsuch as by ammonium hydroxide treatment. Basic treatment as aboveremoves the oligonucleotides from the solid support and cyclizes theimidazole moiety to a 3-deaza-3- reactive functionality!-guanine residuewith the desired oligonucleotide sequence. Further cyclization betweenthe resulting N-2-exocyclic amine group and the aldehydic or ketoniccarbonyl provides tricyclic heterocycle with reactive functionality,(pyrrolo y2,3-β!-imidazo 2,3-δ!pyridin-2-one (5H)-7-(or 8)- reactivefunctionality!). Alternately, cleavage from the support with concentrateammonium hydroxide directly cyclizes the imidazole carboxamide to the3-deazaguanine.

Direct deoxyribosylation of 6-isobutryl pyrrolo 2,3-δ! imidazo 2,3-δ!pyridine 7-(or 8)- reactive functionality! provides the1-(2'-deoxy-β-D-erythro-pentofuransyl) derivative after basic deblockingof the toluoyl groups. The tricyclic heterocycle can be obtained fromthe alkylation of the tetrahydropyranyl derivative of methyl5-cyanomethylimidazole 4-carboxylate in accordance with the procedure ofthe Journal of Medicinal Chemistry, Vol. 21, p. 1212 (1978), withα-halo-α- reactive functionality!-acetaldehyde dimethyl-ketals orα-halomethyl- reactive functionality! ketones with subsequent amination.Acid treatment removes the tetrahydropyranyl blocking group and reducingconditions provides the 7,8-di-hydro 7-(or 8)- reactive functionality!tricyclic heterocycle. The dihydropyrrole ring nitrogen can be protectedwith an isobutryl group. The 5'-DMT-3'-phosphoramidite-6-isobutrylnucleoside can be inserted into sequence-specific oligonucleotides viastandard automated synthesis. Oligonucleotides prepared in this mannercontain a pyrrolo 2,3-b!imidazo 2,3-d!-pyridin-4-one (5H)-7-(or 8)-reactive functionality!, the 7,8-dihydro ring replacing a normal guanineresidue.

In another aspect of the invention, oligonucleo-tides or oligonucleotideanalogs incorporating the novel compounds of the invention are provided.Generally, the oligonucleotides or oligonucleotide analogs may comprisea sugar modified or native oligonucleotide containing a target sequencethat is specifically hybridizable with a preselected nucleotidesequence, a sequence of DNA or RNA that is involved in the production ofproteins whose synthesis is ultimately to be modulated or inhibited inentirely, of single stranded or double stranded DNA or RNA molecule andwhich is nuclease resistant.

Oligonucleotides or oligonucleotide analogs incorporating the novelcompounds of the invention may be synthesized, conveniently throughsolid state synthesis of known methodology, to be complementary to or atleast to be specifically hybridizable with the preselected nucleotidesequence of the RNA or DNA. Nucleic acid synthesizers are commerciallyavailable and their use is generally understood by persons of ordinaryskill in the art as being effective in generating nearly anyoligonucleotide of reasonable length which may be desired. Anoligonucleotide or oligonucleotide analog may then be constructed on asynthesizer incorporating one or more of the 5-cyano- reactivesubstituent!-methyl imidazole compounds in its sequence.

The resulting novel oligonucleotides or oligonucleotide analogs aresynthesized by the standard solid phase, automated nucleic acidsynthesizer such as the Applied Biosystems, Incorporated 380B orMilliGen/Biosearch 7500 or 8800. Triester, phosphoramidite, or hydrogenphosphonate coupling chemistries, M. Caruthers, Oligonucleotides.Antisense Inhibitors of Gene Expression., pp. 7-24, J. S. Cohen, ed.(CRC Press, Inc. Boca Raton, Fla. 1989), are used in with thesesynthesizers to provide the desired oligonucleotides or oligonucleotideanalogs. The Beaucage reagent, Journal of American Chemical Society,Vol. 112, pp. 1253-1255 (1990) or elemental sulfur, S. Beaucage et al.,Tetrahedron Letters, Vol. 22, pp. 1859-1862 (1981), is used withphosphoramidite or hydrogen phosphonate chemistries to providesubstituted phosphorothioate oligonucleotides.

The oligonucleotides or oligonucleotide analogs may further comprise areactive portion appended to the novel base portion; this reactivefunctionality may be attached to the base with a tether group. Forexample, the oligonucleotide or oligonucleotide analogs may furthercomprise a reactive portion capable of catalyzing, alkylating, orotherwise effecting the cleavage of RNA, especially of itsphosphodiester bonds. This reactive portion may be connected to thetargeting portion by a tether. The reactive functionalities may eitherbe basic, acidic, or amphoteric. Heteroatomic species can be formulatedto be either basic or acidic or, indeed, to be amphoteric for suchpurposes. Alkylating and free radical forming functionalities may alsobe used for these purposes. These functionalities are disclosed as setforth in PCT Application Number PCT\US91\00243 assigned to a commonassignee hereof, entitled "Compositions and Methods for Detecting andModulating RNA Activity and Gene Expression," the disclosures of whichare incorporated herein by reference to disclose more fully suchfunctionalities.

These oligonucleotide compositions comprise a targeting portionspecifically hybridizable with a preselected nucleotide sequence of RNA,some of the phosphodiester bonds may be substituted with a structurethat functions to enhance the compositions' ability to penetrate intocells' intracellular region where the RNA, whose activity is to bemodulated, is located. Such substitutions comprise phosphorothioatebonds, short chain alkyl, cycloalkyl structures, structures that aresubstantially non-ionic and non-chiral. Phosphodiester bondmodifications are disclosed as set forth in U.S. patent applicationsassigned to a common assignee hereof, entitled "Backbone Modifiedoligonucleotide Analogs," Ser. No. 703,169 and "Heteroatomicoligonucleotide Linkages," Ser. No. 903,160, the disclosures of whichare incorporated herein by reference to disclose more fully suchmodifications. Backbone modifications may be used without departing fromthe spirit of the invention.

As will be appreciated by persons of ordinary skill in the art,variations in the structures of the sugar moieties useful in thepreparation of the subject compositions may be made without deviatingfrom the spirit of the invention. Suitable substituents on the sugarmoiety include, but are not limited to, O,H, lower alkyl, substitutedlower alkyl, aralkyl, heteroalkyl, heterocycloalkyl, amino-alkylamino,heterocycloalkyl, polyalkylamino, substituted silyl, F, Cl, Br, CN, CF₃,OCF₃, OCN, O-alkyl, S-alkyl, SOMe, SO₂ Me, ONO₂, NO₂, N₃, NH₂, NH-alkyl,OCH₂ CH═CH₂, OCH₂ CCH, OCCHO, or an RNA cleaving moiety. Generally,substituted sugars may be synthesized according to methods disclosed inPCT Patent Application Number PCT\US91\00243 assigned to a commonassignee hereof, entitled "Compositions and Methods for Detecting andModulating RNA activity and Gene Expression," the disclosures of whichare incorporated herein by reference to fully disclose suchmodifications. See also Motawai, supra.

Once again, it is not necessary that every sugar linking function be ina modified form a substantial number and even a predominance of suchlinking groups may exist in he native, phosphodiester form as long asthe overall targeting portion of the compositions of the moleculesexhibits an effective ability to penetrate into the intracellular spacesof cells of the organism in question or otherwise to contact the targetRNA and to specifically bind therewith to form a hybrid capable ofdetecting and modulating the RNA activity. Of course, fully unmodified,native phosphodiester structure as well.

Modifications that may provide oligonucleotides or analogs that aresubstantially less ionic than native forms and facilitate penetration ofmodified or unmodified oligonucleotides into the intracellular spacesare also contemplated by this invention. Any of the existing or yet tobe discovered methods for accomplishing this goal may be employed inaccordance with the practice of the present invention. As will beappreciated by those skilled in the art, modifications of the phosphatebond find utility in this regard. Variations in the phosphate backboneuseful in the preparation of the subject compositions may be madewithout deviating from the spirit of the invention. Modifications at thephosphorous atom are set forth in an application having U.S. applicationSer. No. 558,663 and assigned to a common assignee hereof, saidapplication being entitled "Polyamine Oligonucleotides to EnhanceCellular Uptake," filed Jul. 27, 1990 the modification of the sugarstructure including the elimination of one of the oxygen functionalitiesmay permit the introduction of such substantially non-chiral, non-ionicsubstituents in this position.

Standard backbone modifications such as substituting P for S, Me-P,MeO-P, H₂ N-P, etc. These substitutions are thought in some cases toenhance the sugar modified oligonucleotide properties. Suchsubstitutions include, but are not limited to, phosphorothionate, methylphosphonate, or alkyl phosphate. Backbone modifications are disclosed asset forth in U.S. patent applications assigned to a common assigneehereof, entitled "Backbone Modified Oligonucleotide Analogs," Ser. No.703,619 and "Heteroatomic Oligonucleotide Linkages," Ser. No. 903,160,the disclosures of which are incorporated herein by 10 reference inorder to disclose more fully such modifications. The entirety of thedisclosure of these applications are incorporated herein by reference inorder to disclose more fully such modifications.

The present invention is further described in the following examples.These examples are for illustrative purposes only, and are not to beconstrued as limiting the appended claims.

EXAMPLE 1

Chromatography and Purification.

Silica gel used for flash chromatography was ICN 60 (Costa Mesa,Calif.), 32-63 mesh. Materials not soluble in the solvent system usedfor flash chromatography (FC) were co-evaporated onto E. Merck silicagel 100 (Darmstadt, Republic of Germany), 70-230 mesh, using a suitablesolvent. The dry materials were then applied to the top of a FC column.TLC was performed on prescored E. Merck Kieselgel 60 F₂₅₄ plates.Compounds were visualized by illuminating TLC plates under UV light (254nm) and/or by spraying with 10 methanolic H₂ SO₄ followed by heating.Evaporations were carried out at 40°-50° C. using a rotary evaporatorand a vacuum pump coupled to a vacuum controller. ¹ H-NMR spectra wereobtained at 400 mHz in dmso-d₆ unless otherwise noted. Where relevant,treatment of samples with D₂ O recorded exchangeable protons. Infraredspectra were recorded on a Perkin-Elmer 16PC FT-IR spectrophotometer.Solvent system A=ethyl acetate-hexanes, 3:2; B=ethyl acetate-methanol,9:1, v/v.

EXAMPLE 2

Synthesis of methyl5-(cyanomethyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate

A large scale synthesis of the methyl5-(cyanomethyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate, a starting material for this work was carriedout according to the sodium-salt glycosylation procedure described inRevenkar, supra.

EXAMPLE 3

Synthesis of methyl5-(cyanomethyl)-3-tetrahydropyranyl-imidazole-4-carboxylate Methyl5-cyanomethyl-3-tetrahydropyranyl-imidazole-4-carboxylate was preparedand separated from its positional isomer according to the proceduredescribed in Cook, J. Med. Chem., supra.

EXAMPLE 4

Synthesis of 2'-deoxy-3-deazaguanosine(6-amino-1-(2-deoxy-β-D-ezythro--pentofuranosyl) imidazo4,5-c!pyridin-4(5R)-one.

A small scale synthesis of the 2'-deoxy-3-deazaguanosine(6-amino-1-(2-deoxy-β-D-erythro-pentofuranosyl) imidazo4,5-c!pyridin-4(5H)-one yielded material identical in every respect withthat reported in Revenkar, supra. The alkylation procedures describedbelow yield diastereomeric mixtures differing in configuration at thealkylated (methene) carbon. For the nucleosides, these mixtures exhibitwell-resolved signals for their H-2, methene, H1' and other protons intheir 400 mHz ¹ H-NMR spectra.

EXAMPLE 5

General Nucleoside Alkylation Method. Methyl 5-(cyanononyl!methyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-eythro-pentofuranosyl)imidazole-4-carboxylate

A solution of methyl5-(cyanomethyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate (5.7 g, 11 mmol) in anhydrous acetonitrile (75mL) was treated with sodium hydride (0.88 g, 60% in oil, washed withhexanes) at room temperature and under an atmosphere of argon. Thissuspension was stirred for 15 minutes and then treated with iodononane(7.5 mL, 37.4 mmol) via syringe. The reaction mixture was stirred underthese conditions for 6 hr; thin layer chromatography showed thedisappearance of starting material nucleoside (Rf=0.45, solvent A) andthe appearance of two closely migrating and faster products (Rf=0.65,avg). The reaction was quenched with the addition of glacial acetic acidto pH 5 and then evaporated to dryness in vacuo to afford a yellowsyrup. The syrup was redissolved in dichloromethane (150 mL) and thesolution was washed with cold 0.1N HCl, water, and then dried overmagnesium sulfate. Filtration and evaporation of the organic layerafforded a yellow gum which was purified using FC on silica gel (120 g)using a gradient of ethyl acetate in hexanes (20 to 50%). Fractionscorresponding to the alkylated products were pooled and evaporated toyield Methyl 5-(cyanononyl!methyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate as a foam, 2.9 g (47%). ¹ H-NMR: δ,8.18 and 8.15(s,s; 1 H; H-2); 6.48 and 6.37 (t,t; 1 H; H1'); 4.68 and 4.36(2 m, 1 H,methene); 3.32 (s, 3H, COOCH₃); 2.05, 1.75, 1.18 and 0.90(4 m; 19 H;nonyl). IR (film): 2240 cm-¹ (CN). Anal. Calcd for C37H45N307 (643.778):C, 69.03, H, 7.04, N, 6.53. Found: C, 68.77, H, 6.97, N, 6.39.

The bulkiest 3-C substituent on the 3-deazapurine ring system inducesthe compounds into an unnatural 3'-endo/high-anti (-sc) conformation.Two-dimensional NMR experiments (2D-NOESY) indicate that substituted2'-deoxy-3-deazaguanosines prefer the anti-conformation. The bulkysubstituent in 2'-deoxy-3-(2- 1-naphthyl!ethyl)-3-deazaguanosine appearsto force the sugar into an unusual 3'-endo conformation. Graduallydecreasing the size of these substituents is expected to increase theequilibrium population of the sugar towards 2'-endo. These structuralchanges may be correlated with biological activity; it is reasonable toexpect that the 2'-deoxy-3-alkyl(aryl)-3-deazapurines might be enhancedsubstrates for viral kineses due to their preference for theanti-conformation.

The 2'-deoxy-3-alkyl(aryl)-3-deazaguanosines have uv spectra with nearlyidentical maxima to that of 2'-deoxy-3-deazaguanosine. Also, theirproton NMR exhibit H-2 (IUPAC numbering) aromatic resonances at δ7.9 to8.0 ppm, compared to 7.9 ppm for2'deoxy-3-alkyl(aryl)-3-deazaguanosines, evidence of the nearlynegligible electronic contributions from these alkyl or arylsubstitutions to the overall purine ring current. However, the 2D-NOESYNMR spectrum of 2'-deoxy-3-(2- 1-naphthyl! ethyl)-3-deazaguanosine,(7-(2- 1-naphthyl! ethyl)-6-amino-1-(2deoxy-β-D-erythro-pentofuranosyl)imidazo 4,5)-c!pyridin-4(5H)-one, in dmso-d reveals some interestingfeatures. Poonian, supra. The cross-peaks for the imidazole H-2 andsugar H-3'-protons are strong and there are weak cross peaks for the H-2and H-2' protons. In addition, the H-2" (α) signal appears upfield ofthe H-2' (β) signal, a configuration not normally registered for2'-deoxynucleosides. Taken together, these observations indicate thatthe pseudorotation, Saenger, supra, of the sugar strongly favors 3'-endo(75%) and that this conformation forces the H-2" proton into theshielding volume of the heterocyclic rings. The relative populations of2' and 3-endo conformations of the nucleosides were determined fromtheir 2D-NOESY spectrum, by measurement of the volume of the cross peaksof H-2 and H-2' (β) versus H-2 and H-3' and divided by the sum of bothcross peak volumes. An absence of NOE signals for the N-H imino and3'-protons indicate that this and other nucleosides in this seriesappear to exist strictly in an anti conformation. Rosenmeyer, et al., J.Org. Chem., 1990, 55, 5784. Further, because there is a strong NOEsignal from H-2 and H-1', it appears that this nucleoside is virtuallylocked into a high-anti (-sc) conformation. In contrast, the 2D-NOESYspectrum for the 2'-deoxy-3-allyl-3-deazaguanosine(7-allyl-amino-1-(2-deoxy-β-D-erythro-pentofuranosyl) imidazo4,5c!pyridin-4(5H)-one) exhibits strong cross-peaks for the imidazoleH-2 and sugar H-2' protons and lesser cross peaks for H-2 and H-3'₁,indicating 2'-endo (62%) as a predominant conformation for thedeoxyribose sugar.

EXAMPLE 6

Synthesis of Methyl 5-(allylcyano!methyl)-1-(2'deozy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate

A solution of methyl5-(cyanomethyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate (5.0 g, 9.7 mmol) in anhydrous acetonitrile (75mL) was treated with sodium hydride (0.46 g, 11.6 mmol) and then allylbromide (2.5 mL, 29 mmol). Workup of the reaction and purification ofthe products on silica gel (75 g) as described in Example 1 affordedmethyl 5-(allylcyano!methyl)-1-(2'deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylates a yellowish foam, 3.7 g (68%). ¹ H-NMR (200mHz): δ,8.15 and 8.13 (s,s; 1 H; H-2); 6.38 (m, 1H; H1'); 5.75 and 5.08(2m; 3H; vinyl); 3.79 (s, 3H, COOCH₃). Anal. Calcd for C₃₂ H₃₁ N₃ O₇(557.60): C, 25 66.77, H, 5.60, N, 7.53. Found: C, 66.43; H, 5.59, N,7.38.

EXAMPLE 7

Synthesis of Methyl 5-(benzyl cyano!methyl)-1-(2'-deoxy-3,5di-o-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate

A solution of methyl5-(cyanomethyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate (5.0 g, 9.6 mmol) in anhydrous acetonitrile (75mL) was treated with sodium hydride (0.46 g, 11 mmol) under argon andstirred at room temperature for 15 minutes. The mixture was cooled to 4°C. in an ice bath and a solution of benzyl bromide (1.26 mL, 10.6 mmol)in acetonitrile (15 mL) was added dropwise over 70 min. The ice bath wasremoved and the reaction further stirred at room temperature for 2.5hours. Workup of the reaction and purification of the products on silicagel (100 g) as described in the Example 1 afforded methyl 5-(benzylcyano!methyl)-1-(2'-deoxy-3,5di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate as a white foam, 3.4 g (58%). ¹ H-NMR: δ,8.12and 8.05 (s,s; 1H; H-2); 8.0-7.10 (m, 13 H; aromatic); 6.33 and 6.01(t,t; 1H; H-1'); 5.22 and 5.02 (t,t; 1H; methene); 3.80 (s, 3H, COOCH₃).IR (film): 2240 cm⁻¹ (nitrile). Anal. Calcd for C₃₅ H₃₃ N₃ O₇ (607.66):C, 69.18; H, 5.47; N, 6.92. Found: C, 69.15; H; 5.43; N, 6.82.

EXAMPLE 8

Synthesis of Methyl 5-(cyano2-(1-naphthyl)ethyl!methyl)-1-(2-deoxy-3,5di-O-p-β-D-erythro-pentimidazole-4-carboxylate

A solution of methyl 5-(cyanomethyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl) imidazole-4-carboxylate(7.43 g, 14.3 mmol) in anhydrous acetonitrile (50 mL) was treated withsodium hydride (1.15 g, 28.7 mmol) under argon and stirred at roomtemperature for 15 minutes. The 2-(1-naphthyl)ethyl bromide (16.9 g,71.5 mmol) was added neat and the reaction stirred for 18 hours. Workupof the reaction as described in Example 5 and purification of theproducts on silica gel (150 g), as described in Example 1, using agradient of ethyl acetate in hexanes (20 to 60%) yielded three majorfractions. Fraction 1(1.55 g) contained the faster isomer; fraction2(0.90 g) contained a mixture of both isomers; fraction 3(1.53 g)contained the slower isomer. Overall yield of methyl 5-(cyano2-(1-naphthyl)ethyl!methyl)-1-(2-deoxy-3,5di-O-p-β-D-erythro-pentofuranosyl) imidazole-4-carboxylate, 3.9 g, 42%.Fraction 1. ¹ H-NMR: δ,8.17 (s, 1H, C(2)-H); 7.9-7.1 (m, 15H, aromatic);6.38 (t, 1H, H-1'); 5.17 (t, 1H, methene); 3.72 (s, 3H, COOCH₃).Fraction 3. δ,8.15 (s, 1H, H-2); 7.9-7.1 (m, 15H, aromatic);. 6.26 (t,1H, H-1'); 4.82 (t, 1H, methene); 3.77 (s, 3H, COOCH₃). Anal. Calcd forC₄₀ H₃₇ N₃ O₇ (671.75): C, 71.52; H, 5.55; N, 6.26. Found: C,71.76; H,5.54; N, 6.02.

EXAMPLE 9

General Ammonolysis Method. 5-(Cyano nonyl!methyl)-1-(2'deoxy-β-D-eythro-pentofuranosyl) imidazole-4-carboxamide

The nucleoside methyl 5-(cyanononyl!methyl)-1-(2,'-deoxy-3,5-di-O-p-totuoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate (2.98 g, 4.6 mmol) was dissolved in anhydrousmethanol (5 mL) and transferred to a stainless steel bomb. The solutionwas cooled to -78° C. and then treated with anhydrous liquid ammonia (45mL). The bomb was sealed and then heated to 100° C. in an oil bath for21 hours. TLC (solvent B) exhibited products Rf=0.45, and toluamideRf=0.85, indicating a complete removal of the toluoyl protecting groups.Ammonia was evaporated at room temperature and the amber gum whichresulted was flash chromatographed on silica gel (80 g) using a gradientof methanol in ethyl acetate (5 to 10%). Fractions corresponding to theproducts were pooled and evaporated in vacuo to yield 5-(Cyanononyl!methyl)-1-(2'deoxy-β-D-erythro-pentofuranosyl)imidazole-4-carboxamide as a white foam, 1.2 g (63%). ¹ H-NMR: δ,8.09.and 8.05 (s,s; 1H; H-2); 6.14 (t, 1H; H1'); 5.45 and 5.32(2 dd, 1H,methene); 2.10,1.80,1.40-1.05 and 0.82(4m, 19H; nonyl). Anal. Calcd. forC20H32N404 (392.50): C, 61.20; H, 8.22; N, 14.27. Found: C, 60.97; H,8.24; N, 13.98.

EXAMPLE 10

Synthesis of 5-(Allylcyano!methyl)-1-(2'-deoxy-β-D-eythro-pentofuranosyl)-imidazole-4carboxamide

The nucleoside methyl 5-(allylcyano!methyl)-1-(2'deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate (3.95 g, 7.08 mmol) was treated with liquidammonia and heated to 100° C. in a stainless steel bomb for 8 hours. Theproducts of this reaction were worked up and purified on silica gel (80g) as described in Example 1. The deprotected compound 5-(allylcyano!methyl)-1-(2'-deoxy-β-D-erythro-pentofuranosyl)-imidazole-4carboxamide was isolated as a white foam, 1.3 g (58%). ¹ H-NMR: δ,8.09and 8.05 (s,s; 1 H; H-2); 6.15 (t, 1 H; H1'); 5.75 and 5.10 (2 m, 3 H;vinyl); 5.42 and 5.34 (t,t; 1 H; methene). Anal. Calcd for C₁₄ H₁₈ N₄ O₄(306.33): C, 54.89; H, 5.92; N, 18.29. Found: C, 54.58; H, 5.92; N,17.93.

EXAMPLE 11

Synthesis of 5-(Benzylcyano!methyl)-1-(2'-β-D-eythro-pentofuranosyl)-imidazole-4-carboxamide

The nucleoside methyl 5-(benzyl cyano!methyl)-1-(2'-deoxy-3,5di-o-p-toluoyl-β-D-erythro-pentofuranosyl) imidazole-4-carboxylate (3.0g, 4.93 mmol) was treated with liquid ammonia and heated to 100° C. in astainless steel bomb for 6 hours. The products of this reaction wereworked up and purified on silica gel (80 g) as described in Example 1.The deprotected compound 5-(benzylcyano!methyl)-1-(2'-β-D-erythro-pentofuranosyl)-imidazole-4-carboxamidewas isolated as a white foam, 1.0 g (59%). ¹ H-NMR: δ,8.05 and 8.03(s,s; 1H; H-2); 7.25 (m; 5H; phenyl); 6.17 and 6.07 (t,t; 1H; H1'); 5.50and 5.42 (t,t; 1H; methines). Anal. Calcd for C₁₈ H₃₃ N₃ O₇ (357.39): C,60.49; H, 5.92; N, 15.68. Found: C, 60.65; H, 5.69; N, 15.23.

EXAMPLE 12

Synthesis of 5-(Cyano2-(1-naphthyl)ethyl!methyl)-1-(2deoxy-β-D-erythro-pentofuranosyl)-imidazole-4-carboxamide

The nucleoside methyl 5-(cyano 2-(1-naphthyl)ethyl!methyl)-1-(2-deoxy-3,5di-O-p-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate (3.78 g, 5.76 mmol) was treated with liquidammonia and then heated to 100° C. in a stainless steel bomb for 20hours. The products of this reaction were worked up and purified onsilica gel (86 g) as described in Example 1. The deprotected compound5-(cyano 2-(1-naphthyl)ethyl!methyl)-1-(2deoxy-β-D-erythro-pentofuranosyl)-imidazole-4-carboxamidewas isolated as a white foam, 1.2 g (49%). ¹ H-NMR: δ,8.14 and 8.08(s,s; 1H; H-2); 8.0-7.3 (m, 7H; naphthyl); 6.22 and 6.19 (t,t; 1H; H1');5.55 and 5.30 (t,t; 1H, methene). Anal. Calcd for C₂₃ H₂₄ N₄ O₄(420.47): C, 65.70; H, 5.75; N, 13.32. Found: C, 65.78; H, 5.72; N,13.05.

EXAMPLE 13

General Cyclization Method.6-Amino-7-nonyl-1-(2-deoxy-β-D-ezythro-pentofuranosyl) imidazo4,5-c!pyridin-4(5H)-one (2'-Deoxy-3-nonyl-3-deazaguanosine)

A solution of the nucleoside 5-(cyanononyl!methyl)-1-(2'deoxy-β-D-erythro-pentofuranosyl)imidazole-4-carboxamide(250 mg) in 35 mL methanolic ammonia(saturated at -20° C.) was heated to95° C. in a sealed vessel for 18 hours. The mixture was evaporated toafford a dark solid which was redissolved in hot ethanol. The solidwhich separated upon cooling was filtered and dried in vacuo for 18hours to afford 2'-Deoxy-3-nonyl-3-deazaguanosine (180 mg, 72%) as anamorphous solid. MP 150° C. dec. ¹ H-NMR: δ,10.3 (bs, 1H, N-H); 7.90 (s,1H, H-8); 6.08 (pseudo t, 1H, H-1', J=6.0 Hz); 5.15 (bs, 2H, NH₂); 2.52,1.30 and 1.82(3 m, 19H, nonyl). UV, .sup.λ max,^(nm), (log ε): MeOH,312(4.001), 278(4.040); pH 1, 322(3.687), 296 (3.845); pH 7, 308(2.811),276(2.842); pH 12,290(3.978). Anal. Calcd for C₂₀ H₃₂ N₄ O₄ (392.50): C,61.20; H, 8.22; N, 14.27. Found: C, 61.02; H, 8.20; N, 14.22.

EXAMPLE 14

Synthesis of 7-Allyl-6-amino-1-(2deoxy-β-D-erythro-pentofuranosyl)imidazole 4,5-c!pyridin-4-(5H)-one (2'-deoxy-3-allyl-3-deazaguanosine)

The nucleoside 5-(Allylcyano!methyl)-1-(2'-deoxy-β-D-erythro-pentofuranosyl)-imidazole-4carboxamide (250 mg) was cyclized and purified according to theprocedure described in Examples 13 and 1, respectively, to yield7-Allyl-6-amino-1-(2deoxy-β-D-erythro-pentofuranosyl) imidazole4,5-c!pyridin-4-(5H)-one (2'-deoxy-3-allyl-3-eazaguanosine) (190 mg,76%) as an amorphous solid. MP.155° C. dec. ¹ H-NMR (200 mHz): δ,10.4(bs, 1H, N-H); 7.98 (s, 1H, H-8); 6.05 (pseudo t, 1 H, H1', J=5.4 Hz);5.92, 5.02 and 4.88 (3m, 3H, vinylic); 5.34 (s, 2H, NH₂); 3.40 and 3.19(2m, 2H, allylic). UV, .sup.λ max,^(nm), (log ε): 310 (3.996), 276(4.060); pH 1, 320 (3.891), 292, (4.064); pH 7, 306 (3.963), 274(4.011); pH 12, 288 (4.160). Anal. Calcd for C₁₄ H₁₈ N₄ O₄ (306.32): C,54.89; H, 5.92; N, 18.29. Found: C, 54.58; H, 92; N, 18.09.

EXAMPLE 15

Synthesis of 6-Amino-7-benzyl-1-(2-deoxy-β-D-erythro-pentofuranosyl)imidazo- 4,5c!pyridin 4(5H)-one (2'-deoxy-3-benzyl-3-deazaguanosine

The nucleoside 5-(Benzylcyano!methyl)-1-(2'-β-D-erythro-pentofuranosyl)-imidazole-4-carboxamide(250 mg) was cyclized and purified by trituration with hot ethanol asdescribed in Examples 13 to yield 2'-deoxy-3-benzyl-3-deazaguanosine(200 mg, 80%) as a white solid. MP 140° C. dec. ¹ H-NMR: δ 10.4 (bs, 1H,N-H); 7.84 (s, 1H, H-8); 7.3-7.1 (m, 5H, phenyl); 6.04 (pseudo t, 1H,H-1', J=6.3 Hz); 5.07 (bs, 2H, NH₂); 4.07 and 3.88 (dd, 2H, benzylic,J=17 Hz). UV, .sup.λ max,^(nm), (log ε): MeOH, 310 (3.950), 276 (4.002);pH 1, 320 (3.835), 294 (3.988); pH 7 308 (3.923), 274 (3.959); pH 12,310(3.930). Anal. Calcd for C₁₈ H₂₀ N₄ O₄ (356.38): C, 60.66; H, 5.66; N,15.72. Found: C, 60.15; H, 5.60; N, 15.51.

EXAMPLE 16

Synthesis of 6-Amino 7-(2-1-naphthyl!ethyl)-1-(2deoxy-β-D-erythro-pentofuranosyl) imidazo4,5-c!pyridin-4(5H)-one (2'-deoxy-3-(2-1-naphthyl!ethyl)3-deazaguanosine

The nucleoside 5-(Cyano 2-(1-naphthyl)ethyl!methyl)-1-(2deoxy-β-D-erythro-pentofuranosyl)-imidazole-4-carboxamide(250 mg) was cyclized and purified from hot ethanol as described inExample 13 to yield 6-Amino 7-(2-1-naphthyl!ethyl)-1-(2deoxy-β-D-erythro-pentofuranosyl) imidazo4,5-c!pyridin-4(5H)-one (2'-deoxy-3-(2- 1-naphthyl!ethyl)3-deazaguanosine (200 mg, 80%) as an off-white solid. MP 195° C.dec. ¹ H-NMR: δ,10.5 (bs, 1H, N-H); 7.98 (s, 1H, H-8); 8.2-7.4 (m, 7H,naphthyl); 6.21 (pseudo t, 1H, H-1', J=6.9 Hz); 5.32 (bs, 2H, NH₂);3.3-2.8 (m, 4H, ethylene). UV .sup.λ max,^(nm), (log ε): MeOH,310(4.019), 289(4.180); pH 1,324(3.805), 290(4.114); pH 7,310 (3.611),284(3.834); pH 12,286(4.185). Anal. Calcd for C₂₃ H₂₄ N₄ O₄ (420.47): C,65.70; H, 5.75; N, 13.32. Found: C, 65.80; H, 5.72; N, 13.05.

EXAMPLE 17

General Heterocycle Alkylation Method. Methyl 5-(cyanononyl!methyl)-3-tetrahydropyranyl-imidazole-4-carboxylate

The cyanomethyl imidazole (5.0 g, 20 mmol) was alkylated using NaH (1.2g, 60% in oil, washed with hexanes) and iodononane (7.6 g, 30 mmol) asdescribed in Example 5, the General Procedure for the nucleosides. Theproducts were purified by FC using a gradient of ethyl acetate inhexanes (20 to 50%). Evaporation of the fractions containing theproducts yielded methyl 5-(cyanononyl!methyl)-3-tetrahydro-pyranyl-imidazole-4-carboxylate (5.0 g, 67%)as a yellow foam. ¹ H-NMR (200 mHz): δ,8.22 (s, 1H, H-2); 5.87 (m, 1 H,H-2' tetrahydropyranyl); 4.58 (m, 1H, methene); 3.85 (s, 3H, COOCH₃);1.30 and 0.88(2 m, 19H, nonyl). Anal. Calcd for C₂₁ H₃₃ N₃ O₃ (375.51):C, 67.17; H, 8.86; N, 11.19. Found: C, 67.47; H, 8.95; N, 11.21.

EXAMPLE 18

Synthesis of Methyl 5-(allylcyano!methyl)-3-tetrahydro-pyranyl-imidazole-4-carboxylate

The cyanomethyl imidazole (5.0 g, 20 mmol) was alkylated using NaH (1.2g) and allyl bromide (3.6 g, 30 mmol) and purified according to Examples5 and 1, respectively. White foam, 3.9 g, 67%. ¹ H-NMR (200 mHz): δ,8.23(s, 1H, H-2); 5.87 (m, 1H, H-2' tetrahydropyranyl); 5.77 and 5.15 (2m,3H, vinylic); 5.68 (m, 1H, methene); 3.86 (s, 3H, COOCH₃). Anal. Calcdfor C₁₅ H₁₉ N₃ O₃ : C, 62.27; H, 6.62; N, 14.52. Found: C, 62.27; H,6.62; N, 14.54.

EXAMPLE 19

Synthesis of Methyl 5-(benzylcyano!methyl)-3-tetrahydropyranyl-imidazole-4-carboxylate

The cyanomethyl imidazole (5.0 g, 20 mmol) was alkylated using NaH (1.2g) and benzyl bromide (5.1 g, 30 mmol), as described in Example 5, andpurified according to Example 1. White foam, 4.8 g, 71%. ¹ H-NMR (200mHz): δ,8.25 (s, 1H, H-2); 7.29 (m, 5H, phenyl); 6.83 (m, 1H, H-2'tetrahydropyranyl); 4.84 (m, 1H, methene); 3.84 and 3.80 (s,s; 3H,COOCH₃); 3.19 (m, 2H, benzylic). Anal. Calcd. for C₁₉ H₂₁ N₃ O₃(339.39): C, 67.24; H, 6.24; N, 12.38. Found: C, 67.21; H, 6.19; N,12.02.

EXAMPLE 20

Synthesis of Methyl 5-(cyano2-(1-naphthyl)ethyl!methyl)-3-tetrahydropyranyl -imidazole-4-carboxylate

The cyanomethyl imidazole (5.0 g, 20 mmol) was alkylated using NaH (1.2g) and 2-(1-naphthyl)ethyl bromide (7.1 g, 30 mmol, Frinton Labs,Piscataway, N.J.), as described in Example 5, and purified according tothe procedure discussed in Example 1. White foam, 5.0 g, 62%. ¹ H-NMR(200 mHz): δ,8.23 (s, 1H, H-2); 8.1-7.3 (m, 7H, naphthyl); 5.80 (m, 1H,H-2' tetrahydropyranyl); 4.58 (m, 1H, methene); 3.57 (s, 3H, COOCH₃).Anal. Calcd for C₂₄ H₃₅ N₃ O₃ (403.48): C, 71.44; H, 6.24; N, 10.41.Found: 71.38; H, 6.16; N, 10.45.

EXAMPLE 21

General Nucleoside Cyclization Method.6-Amino-7-nonyl-1,5-dihydroimidazo 4,5-c!pyridin-4-one HydrochlorideSalt

The compound methyl 5-(cyanononyl!methyl)-3-tetrahydropyranyl-imidazole-4-carboxylate (2.5 g, 6.7mmol) was dissolved in 50 mL methanolic ammonia (saturated at -20° C.)in a stainless steel bomb. The mixture was stirred at 75° C. for 72hours and then evaporated to dryness In vacuo. The resulting solid wasco-evaporated with methanol (45 mL) and then immediately stirred withmethanolic 1N HCl (50 mL) for 12 hours. After this time, the reactionmixture was evaporated to afford a light yellow gum. This gum wasprecipitated by repeated co-evaporation with methanol. Amorphous solid,1.1 g, 53%. MP 225 darkens; 240° C. dec. ¹ H-NMR: δ,10.8 (bs, 1H, N-H);8.72 (s, 1H, H-2); 5.80 (bs, 2H, NH₂); 2.0, 0.9 and 0.4(3m, 19H, nonyl).UV, .sup.λ max,^(nm), (log ε): MeOH, 310(3.935), 270(3.969). Anal.Calcd. for C₁₅ H₂₅ N₄ OC1 (312.84): C, 57.59; H, 8.05; N, 17.90. Found:C, 57.53; H, 8.05; N, 17.87.

EXAMPLE 22

Synthesis of 7-Allyl-6-amino-1,5-dihydroimidazo 4,5-c! pyridin-4-oneHydrochloride Salt

The compound methyl 5-(allylcyano!methyl)-3-tetrahydropyranyl-imidazole-4-carboxylate (2.5 g, 8.6mmol) was cyclized and isolated according to the procedure discussed inExample 21. Amorphous solid, 1.3 g, 67%. MP 210° C. dec. ¹ H-NMR: δ,11.0(bs, 1 H, NH); 8.49 (s, 1H, H-2); 5.80 and 4.98(2m, 3H, vinylic); 5.80(bs, 2H, NH₂); 3.26 (m, 2H, allylic). UV .sup.λ max,^(nm), (log ε):MeOH, 310(3.927), 268 (3.985). Anal. Calcd for C₉ H₁₁ N₄ OC1 (226.66):C, 47.69; H, 4.89; N, 24.72. Found: C, 48.04; H, 5.02; N, 23.76.

EXAMPLE 23

Synthesis of 6-Amino-7-benzyl-1,5-dihydroimidazo 4,5c! pyridin-4-oneHydrochloride Salt

The compound methyl 5-(benzylcyano!methyl)-3-tetrahydropyranyl-imidazole -4-carboxylate (2.5 g, 7.4mmol) was cyclized and isolated according to the procedure described inExample 21. Amorphous solid, 1.9 g, 92%. MP 196° C. dec. ¹ H-NMR: δ,11.5(bs, 1 H, N-H); 9.20 (s, 1H, H-2); 7.17 (m, 5H, phenyl); 6.20 (bs, 2H,NH₂); 3.95 (s, 2H, benzylic). UV, .sup.λ max,^(nm), (log ε): MeOH,310(3.958), 268(3.988). Anal. Calcd for C₁₃ H₁₃ N₄ OC1 (276.72): C,56.42; H, 4.73; N, 20.25. Found: C, 56.40; H, 4.71; N, 20.03.

EXAMPLE 24

Synthesis of 6-Amino-7-(2- 1-naphthyl!ethyl)-1,5-dihydro4,5-c!pyridin-4-one Hydrochloride Salt

The compound methyl 5-(cyano2-(1-naphthyl)ethyl!methyl)-3-tetrahydropyranyl-imidazole-4-carboxylate(2.5 g, 6.2 mmol) was cyclized and isolated according to the proceduredescribed in Example 21. Amorphous solid, 1.64 g, 78%. MP 260 darkens,273 ° C. dec. ¹ H-NMR: δ,11.4 (bs, 1H, N-H); 9.20 (s, 1H, H-2); 8.1-7.4(m, 7H, naphthyl); 6.10 (bs, 2H, NH₂); 3.15 and 3,02 (2 m, 4H,ethylene). UV, ⁸⁰ max,^(nm), (log ε): MeOH, 308 (3.930), 272 (4.137).Anal. Calcd for C₁₈ H₁₇ N₄ OC1 (340.81): C, 63.18; H, 4.95; N, 16.28.Found: C, 63.18; H, 4.95; H, 16.28.

EXAMPLE 25

Synthesis of 6-Amino-1,5-dihydro 4,5-c!pyridin-4-one (3-Deazaguanine)Hydrochloride Salt

The compound cyanomethyl imidazole (2.5 g, 10 mmol) was cyclized and theproduct isolated according to the procedure described in Example 21.This compound gave a satisfactory ¹ H-NMR but proved unstable duringpurification and did not fit C,H,N analysis as a hydrochloride salt,Hartman, supra: ¹ H-NMR: δ,10.5 (bs, 1H, N-H); 8.18 (s, 1H, H-2); 5.4(bs, 2H, NH₂); 4.6 (s, 1H, H-7).

EXAMPLE 26

Synthesis of Methyl 5-(cyanononyl!methyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate

A solution of methyl 5-(cyanomethyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate (5.7 g, 11 mmol) in anhydrous acetonitrile (75mL) was treated with sodium hydride (0.88 g, 60% in oil, washed withhexanes) at room temperature and under an atmosphere of argon. Thissuspension was stirred for 15 minutes and then treated with iodononane(7.5 mL, 37.4 mmol) using a syringe. The reaction mixture was stirredunder these conditions for 6 hr; thin layer chromatography plates (ethylacetate/hexanes, 3:2, v/v) showed the disappearance of starting materialnucleoside and the appearance of two faster migrating products. Thereaction was quenched with the addition of glacial acetic acid to pH 5and then evaporated to dryness in vacuo to afford a yellow syrup. Thesyrup was dissolved in dichloromethane (150 mL) and the solution waswashed with cold 0.1N HCl, water, and then dried over magnesium sulfate.Filtration of the desiccant and evaporation of the solvent afforded ayellow gum which was flash-chromatographed on silica gel (120 g) usingethyl acetate-hexanes (1:4 then 1:1). Fractions corresponding to thealkylated products were pooled and evaporated to yield Methyl 5-(cyanononyl!methyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate. as a yellowish foam, 2.98 g (47%). 1H-NMR (Me₂SO-d6): δ, 8.18 and 8.15 (s,s; C-2 H, 1 H); 6.48 and 6.37 (t,t; H-1', 1H); 1.18 and 0.90 (2 m, nonyl, 19 H).

EXAMPLE 27

Synthesis of Methyl 5-(allylcyano!methyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate

A solution of methyl5-(cyanomethyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate (5.0 g, 9.7 mmol) in anhydrous acetonitrile (75mL) was treated with sodium hydride (0.46 g, 11.6 mmol) and then allylbromide (2.5 mL, 29 mmol) in the manner described for in Example 29. Thereaction was worked up and chromatographed on silica gel (75 g) usingthe aforementioned solvent system to afford 84 as a yellowish foam, 3.66g (68%). 1H-NMR (Me₂ SO-d6):δ,8.15 and 8.13 (s,s; C-2 H, 1 H); 6.38 (m,H-1', 1 H); 5.75 and 5.08 (2 m, vinyl, 3 H).

EXAMPLE 28

Synthesis of Methyl 5-(benzylcyano!methyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate

A solution of methyl5-(cyanomethyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate (5.0 g, 9.6 mmol) in anhydrous acetonitrile (75mL) was treated with sodium hydride (0.46 g, 11 mmol) under argon andstirred at room temperature for 15 minutes. The mixture was cooled to 4°C. in an ice bath and a solution of benzyl bromide (1.26 mL, 10.6 mmol)in acetonitrile (15 mL) was added dropwise over 70 min. The ice bath wasremoved and the reaction further stirred at room temperature for 2.5hours. Workup of the reaction and purification of the products on silicagel (100 g) afforded methyl 5-(benzylcyano!methyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate. as a white foam, 3.4 g (58%). 1H-NMR (Me₂SO-d6): δ,8.10 and 8.05 (s,s; C-2 H, 1 H); 7.30-7.10 (m, phenyl, 5 H);5.33 and 6.01 (t,t; H-1', 1 H).

EXAMPLE 29

Synthesis of 5-(Cyanononyl!methyl)-1-(2'-deoxy-β-D-erythropento-furanosyl)imidazole-4-carboxamide

The nonyl-imidazole nucleoside, methyl 5-(cyanononyl!methyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate, (2.98 g, 4.6 mmol) was dissolved in anhydrousmethanol (5 mL) and trans-ferred to a stainless steel bomb. The solutionwas cooled in a dry-ice /isopropanol bath and then treated withanhydrous liquid ammonia (45 mL). The bomb was sealed and then heated to100° C. in an oil bath for 21 hours. TLC (ethyl acetate/methanol, 4:1,v/v) indicated a complete removal of the toluoyl protecting groups.Excess ammonia was evaporated at room temperature and the amber gumwhich resulted was flash chromatographed on silica gel (80 g) usingethyl acetate/methanol (95:5 then 9:1). Fractions corresponding todeblocked products were pooled and evaporated in vacuo to yield 5-(cyanononyl!methyl)-1-(2'-deoxy-β-D-erythropento-furanosyl)imidazole-4-carboxamide as a white foam, 1.14 g (63%). 1H-NMR (Me₂SO-d6):δ,8.09 and 8.05 (s,s; C-2 H, 1 H); 6.14 (t, H-1', 1H); 1.40-1.05and 0.95 (2 m, nonyl, 19 H).

EXAMPLE 30

Synthesis of 5-(Allylcyano!methyl)-1-(2'-deozy-β-D-erythropento-furanosyl)imidazole-4-carboxamide

The allyl-imidazole nucleoside methyl 5-(allylcyano!methyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole-4-carboxylate (3.95 g, 7.08 mmol) was treated with liquidammonia in a stainless steel bomb and heated to 100° C. for 8 hours. Theproducts of this reaction were worked up and purified on silica gel (80g) in a manner analogous to that for compound synthesized according toExample 32, 5-(Cyanononyl!methyl)-1-(2'-deoxy-β-D-erythropento-furanosyl)imidazole-4-carboxamide. The de-blocked compound synthesized accordingto Example 33, 5-(Allylcyano!methyl)-1-(2'-deoxy-β-D-erythropento-furanosyl)imidazole-4-carboxamide, was isolated as a white foam, 1.29 g (58%).1H-NMR (Me₂ SO-d6):δ,8.09 and 8.07 (s,s; C-2 H, 1 H); 6.15 (t, H-1', 1H); 5.75 and 5.10 (2 m, vinyl, 3 H).

EXAMPLE 31

Synthesis of 5-(Benzylcyano!methyl)-1-(2'-deoxy-β-D-erythropento-furanosyl)imidazole-4-carboxamide

The benzyl-imidazole nucleoside synthesized according to Example 31 (3.0g, 4.93 mmol) was treated with liquid ammonia in a stainless steel bomband heated to 100° C. for 6 hours. The products of this reaction wereworked up and purified on silica gel (80 g) in a manner analogous tothat for compound synthesized according to Example 32. The deblockedcompound synthesized according to Example 34 was isolated as a whitefoam, 1.03 g (59%). 1H-NMR (Me₂ SO-d6): δ,8.03 and 8.04 (s,s; C-2 H, 1H); 7.25 (m, phenyl, 5 H); 6.17 and 6.07 (t,t; H-1', 1 H).

EXAMPLE 32

Synthesis of5-(cyanomethyl)-1-(2'-deoxy-5'-O-dimethoxytrityl-β-D-erythropentofuranosyl)imidazole-4-carboxamide

The nucleoside, methyl5-(cyanomethyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole -4-carboxamide, (1.95 g, 7.3 mmol) was dried by co-evaporationwith pyridine (30 mL). The gum which resulted was dissolved in anhydrouspyridine under argon and then treated with dimethoxytrityl chloride(2.90 g, 12.4 mmol). The mixture was stirred at room temperature for 2hours after which TLC (ethyl acetate:methanol, 19:1, v/v) indicatedcomplete conversion of starting material. Tritylated products werevisualized as orange spots using H₂ SO₄ fumes. The reaction was quenchedwith the addition of methanol (2 mL) followed by stirring for 15 min.The mixture was evaporated in vacuo to afford a thick orange syrup whichwas co-evaporated with toluene (3×25 mL). The syrup was flashchromatographed on silica gel (100 g) using a stepwise gradient ofmethanol in 1% Et₃ N/CH₂ Cl₂ (0 to 5% methanol). The appropriatefractions were pooled and evaporated to yield5-(Cyanomethyl)-1-(2'-deoxy-5'-O-dimethoxytrityl-β-D-erythropentofuranosyl)imidazole-4-carboxamide as a white foam, 3.64 g (87%). 1H-NMR (Me₂SO-d6): δ,7.96 (s, C-2 H, 1 H); 6.85-7.35 (m, DMT, 13 H); 6.13 (t, H-1',1 H).

EXAMPLE 33

Synthesis of 5-(Cyanononyl!methyl)-1-(2'-deoxy-5'-O-dimethoxytrityl-β-D-erythropentofuranosyl)imidazole-4-carboxamide

The nucleoside synthesized according to Example 32 (1.20 g, 3.1 mmol)was thoroughly dried by co-evaporation with anhydrous pyridine (30 mL).The syrup which resulted was redissolved in anhydrous pyridine underargon and treated with dimethoxytrityl chloride (1.0 g, 3.1 mMol). Thereaction mixture was stirred at room temperature for 3.5 hr, after whichtime TLC (ethyl acetate) indicated complete conversion of the startingmaterial. The reaction mixture was treated with 2 mL of anhydrousmethanol, stirred for 15 minutes and then evaporated in vacuo to afforda bright orange syrup. This syrup was co-evaporated with toluene (2×50mL) and then flash chromatographed on silica (80 g) using a step-wisegradient of methanol in dichloromethane/1% triethylamine (0 to 3%methanol). The appropriate fractions were pooled and evaporated in vacuoto yield the dimethoxy-tritylated compound 5-(Cyanononyl!methyl)-1-(2'-deoxy-5'-O-dimethoxytrityl-β-D-erythropentofuranosyl)imidazole-4-carboxamide as a white foam, 1.46 g (69%). 1H-NMR (Me₂SO-d6): δ,7.98 and 7.93 (s,s; C-2 H, 1 H); 7.30 and 6.92 (2 m,DMT, 13H); 6.21 (t, H-1', 1 H); 1.20 and 0.92 (2 m, nonyl, 19 H).

EXAMPLE 34

Synthesis of 5-(Allylcyano!methyl)-1-(2'-deoxy-5'-O-dimethoxytrityl-β-D-erythropentofuranosyl)imidazole-4-carboxamide

The nucleoside synthesized according to Example 33 (1.25 g, 4.08 mmol)was dried by co-evaporation with pyridine and then redissolved inanhydrous pyridine (50 mL) and treated with dimethoxy-trityl chloride(1.38 g, 4.08 mmol) under an atmosphere of argon. The reaction wasstirred for 2.5 hours and then worked up and products isolated by flashchromatography on silica gel (90 g) in a manner analogous to compoundsynthesized according to Example 35. The appropriate fractions werepooled and evaporated in vacuo to yield dimethoxytritylated compound 37as a white foam, 1.86 g (75%). 1H-NMR (Me₂ SO-d6):δ,7.98 and 7.95 (s,s;C-2 H, 1 H); 7.25 and 6.93 (2 m, DMT, 13 H); 6.21 (m, H-1', 1 H); 5.78and 5.10 (2 m, vinyl, 3 H).

EXAMPLE 35

Synthesis of 5-(Benzylcyano!methyl)-1-(2'-deoxy-5'-O-dimethoxy-trityl-β-D-erythropentofuranosyl)imidazole-4-carboxamide

The nucleoside synthesized according to Example 34, 930 mg (2.6 mmol)was dried by co-evaporation with pyridine and then redissolved inanhydrous pyridine (50 mL) and treated with dimethoxy-trityl chloride(884 mg, 2.6 mmol) under an atmosphere of argon. The reaction wasstirred for 4 hours and then worked up and the products isolated byflash chromatography on silica gel (80 g) in a manner analogous to thecompound synthesized according to Example 35. The appropriate fractionswere pooled and evaporated in vacuo to yield 1.50 g of 5-(Benzylcyano!methyl)-1-(2'-deoxy-5'-O-dimethoxy-trityl-β-D-erythropentofuranosyl)imidazole-4-carboxamide as a pinkish foam, (87%). 1H-NMR (Me₂SO-d6):δ,7.70 (s, C-2 H, 1 H); 7.40 and 6.70 (2m; DMT, phenyl; 18 H);6.10 (t, H-1', 1 H).

EXAMPLE 36

Synthesis of 5-(Cyanomethyl)-1-(5'-O-dimethoxytrityl-3'-O-2-cyano-ethyl-N,N-diisopropyl!phosphoramidite-2'-deoxy-β-D-erythropentofuranosyl)imidazole-4-carboxamide

The tritylated nucleoside synthesized according to Example 35 (1.82 g,3.2 mmol) was dissolved in anhydrous tetrahydrofuran (50 mL) under argonand then treated with diisopropyl ethylamine (1 mL). The solution wascooled to 4° C. in an ice bath and then treated with2-cyanoethyl-N,N-diisopropyl phosphorochloridate (1.2 g, 5.12 mmol) inone portion. The ice bath was removed and the reaction mixture wasstirred at room temperature for 3 hours. At the end of this time, TLC(CH₂ Cl₂ /1% MeOH/1% Et₃ N) indicated complete conversion of startingmaterial. Reaction products were visualized using H₂ SO₄ fumes. Thereaction mixture was evaporated in vacuo to afford a thick syrup whichwas immediately redissolved in dichloromethane (100 mL) and washed withcold, saturated sodium bicarbonate (2×50 mL) and brine (50 mL). Theorganic layer was dried over magnesium sulfate, filtered and evaporatedto yield a yellowish foam (2.8 g). This foam was flash chromatographedon silica gel (75 g) using a stepwise gradient of ethyl acetate/hexanes(1:4 to 1:1) containing 1% Et₃ N. The appropriate fractions were pooledand evaporated to yield 5-(Cyanomethyl)-1-(5'-O-dimethoxytrityl-3'-O-2-cyano-ethyl-N,N-diisopropyl!phosphoramidite-2'-deoxy-β-D-erythropentofuranosyl)imidazole-4-carboxamide. as a white foam, 1.65 g (59%). An aliquot ofthis material was precipitated by dissolving the foam in a small volumeof dichloromethane and adding it to a large proportion (1:50) ofhexanes. 1H-NMR (CD₃ CN): δ,7.78 and 7.72 (s,s; C-2 H, 1H); 7.25 and6.95 (m, DMT, 13 H); 6.12 (t, H-1', 1H). 31P-NMR (CD₃ CN): δ, 150.02,149.98.

EXAMPLE 37

Synthesis of 5-(Cyano nonyl!methyl)-1-(5'-O-dimethoxytrityl-3'-2-cyanoethyl-N,N-diisopropyl!phosphoramidite-2'-deoxy-β-D-erythropentofuranosyl)imidazole-4-carboxamide

The tritylated nucleoside synthesized according to Example 36, 1.46 g(2.1 mmol) was dissolved in anhydrous tetrahydrofuran (50 mL) underargon and then treated with diisopropyl ethylamine (1.5 mL). Thismixture was cooled to 4° C. in an ice bath and then treated with2-cyanoethyl-N,N-diisopropylamino phosphorochloridite (488 mg, 2.1 mmol)in one portion. The ice bath was removed and the reaction was furtherstirred at room temperature for a total of 3 hours. Additionalphosphorochloridite (48 mg) was added at the end of the first and secondhours of reaction. At the end of this time, TLC (CH₂ Cl₂ /3% MeOH/1% Et₃N) indicated complete conversion of starting material. The reactionmixture was worked up as described for the compound synthesizedaccording to Example 39 and the products purified on silica gel (80 g)using a stepwise gradient of ethyl acetate/hexanes (2:3 to 3:2)containing 1% Et₃ N. The appropriate fractions were pooled andevaporated to afford 5-(Cyanononyl!methyl)-1-(5'-O-dimethoxytrityl-31-0- 2-cyanoethyl-N,N-diisopropyl!phosphoramidite-2'-deoxy-β-D-erythropentofuranosyl)imidazole-4-carboxamide as a colorless foam, 1.37 g (73%). An aliquot ofthis material was precipitated using a procedure described for thecompound synthesized according to Example 39. 1H-NMR (CD₃ CN): δ, 7.75(s, C-2 H); 7.25 and 6.85 (2 m, DMT, 13 H), 6.25 and 6.20 (2 m, H-1', 1H). ³¹ P-NMR (CD₃ CN): δ, 150.1, 150.0 and 149.9.

EXAMPLE 38

Synthesis of 5-(Ally cyano!methyl)-1-(5'-O-dimethoxytrityl-3'-O-2-cyanoethyl-N,N-diisopropyl!phosphoramidite-2'-deoxy-β-D-erythro-pentofuranosyl)imidazole-4-carboxamide

The tritylated nucleoside synthesized according to Example 37, 1.86 g(3.1 mmol) was dissolved in anhydrous THF (50 mL) and then treated withdiisopropyl ethylamine (1.5 mL) and 2-cyanoethyl N,N-diisopropylaminophosphochloridite (705 mg, 3.1 mmol) in a manner analogous to thecompound synthesized according to Example 40. The mixture was stirred atroom temperature for a total of 3 hours. Additional phosphochloridite(140 mg) was added at the end of 2 hour reaction time. The reaction wasworked up and the products isolated by flash chromatography on silicagel (80 g) using a stepwise gradient of ethyl acetate/hexanes (2:3 to4:1, v/v). The appropriate fractions were pooled and evaporated to yield2.18 g (88%) of 41 as a white solid foam. An aliquot of this materialwas precipitated using a procedure described for compound synthesizedaccording to Example 39. 1H-NMR (CD₃ CN): δ, 7.77 and 7.75 (s,s; C-2 H,1 H); 7.45 and 6.85 (2m, DMT, 13 H); 6.25 and 6.20 (t,t; H-1', 1 H).31P-NMR (CD₃ CN): δ, 150.05, 149.98 and 149.85.

EXAMPLE 39

Synthesis of 5-(Benzyl cyano!methyl)-1-(5'-O-dimethoxytrityl-3'-O-2-cyanoethyl-N,N-diisopropyl!phosphoramidite-2'-deoxy-β-D-erythro-pentofuranosyl)imidazole-4-carboxamide

The tritylated nucleoside synthesized according to Example 38, 1.50 g(2.3 mmol) was dissolved in anhydrous THF (50 mL) and then treated withdiisopropyl ethylamine (1.5 mL) and 2-cyanoethyl-N,N-di-isopropylaminophosphochloridite (539 mg, 2.3 mmol) in a manner analogous to thecompound synthesized according to Example 39. The mixture was stirred atroom temperature for a total of 3 hours. Additional phosphorochloridite(110 mg) was added at the end of 2 hours reaction time. The reaction wasworked up and the products isolated by flash chromatography on silicagel (40 g) using a stepwise gradient of ethyl acetate/hexanes (1:4 to3:2, v/v). The appropriate fractions were pooled and evaporated to yield5-(Benzyl cyano!methyl)-1-(5'-O-dimethoxytrityl-3'-O-2-cyanoethyl-N,N-diisopropyl!phosphoramidite-2'-deoxy-β-D-erythro-pentofuranosyl)imidazole-4-carboxamide., 1.03 g (55%) as a colorless foam. An aliquotof this material was precipitated using a procedure described for thecompound synthesized according to Example 39. 1H-NMR (CD₃ CN): δ, 7.72(s,s; C-2 H; 1 H); 7.30 and 6.80 (2 m; DMT, benzyl; 18 H); 6.10 (m,H-1', 1 H). ³¹ P-NMR (CD₃ CN): δ, 150.00, 149.90 and 149.85.

EXAMPLE 40

Synthesis of Oligomers

Oligomers incorporating the nucleotides of Examples 39, 40, 41 and 42were made using standard phorphoramidite chemistries on an AppliedBiosystems 380B synthesizer. Average coupling efficiencies were 94%using a method which left the 5'-dimethoxytrityl group of eacholigonucleotide on. After cleavage from the solid support, the oligomerswere treated with excess concentrated ammonium hydroxide and then heatedin a sealed vessel at 55° C. for a minimum of 15 hours. This procedureremoved all protecting groups from A, G and C bases and causedcyclization of the 5-cyano alkyl!methyl imidazole to the 3-deaza-3-alkyl(or aryl) heterocycles. For each nucleotide, verification of thiscyclization was made from the analysis of a 1H-NMR spectrum of a TG3Ctrimer containing a single 3-deaza-3-substituted 2'-deoxyguanosine base.Purification of these trityl-on oligomers was performed using a C-4Waters Prepak cartridge (10 cm) using a gradient elution of acetonitrilein 50 mM triethyl ammonium acetate (pH 7.0) (4 to 48t over 60 min). Thetrityl group was removed by a treatment with 15% acetic acid and theoligomers were then precipitated from 70% ethanol.

EXAMPLE 41

Synthesis of 5-(Cyanopropylphthalimide!methyl)-1-(5'-O-dimethoxy-trityl-3'-O'2-cyanoethyl-N,N-diisopropyl!phosphoramidite-2'-deoxy-β-D-erythro-pentofuranosyl-imidazole-4-carboxamide

In a manner as per Example 29, the compound methyl5-(cyanomethyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole -4-carboxylate can be treated withN-(3-bromopropyl)phthalimide instead of iodononane. After work-up as perExample 29 the product can be treated as per Examples 35 and 39 to yieldthe 5-(Cyano propylphthalimide!methyl)-1-(5'-O-dimethoxy-trityl-3'-O '2-cyanoethyl-N,N-diisopropyl!phosphoramidite-2'-deoxy-β-D-erythro-pentofuranosyl-imidazole-4-carboxamide.In addition to ring closure upon cleavage from the oligonucleotidesynthesizer solid support, the phthalimide is also cleaved to amino asper other above examples. Further the alkylamino product can be chainextended to a polyalkylamine.

EXAMPLE 42

Synthesis of 5-(Cyanoimidizo-1-yl(propyl)!methyl)-1-(5'-O-dimethoxy-trityl-3'-O'2-cyanoethyl-N,N-diisopropyl!phosphor-amidite-2'-deoxy-β-D-erythro-pentofuranosyl-imidazole-4-carboxamide

In a manner as per Example 29, the compound methyl5-(cyanomethyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole -4-carboxylate can be treated with 1-(3-bromopropyl)imidazoleinstead of iodononane. After work-up as per Example 29 the product canbe treated as per Examples 35 and 39 to yield 5-(Cyano imidizo-1-yl(propyl)!methyl)-1-(5'-O-dimethoxy-trityl-3'-O'2-cyanoethyl-N,N-diisopropyl!phosphoramidite-2'-deoxy-β-D-erythro-pentofuranosyl-imidazole-4-carboxamide.

EXAMPLE 43

Synthesis of 5-(Cyanoanthracen-2-yl(propyl)!methyl)-1-(5'-O-di-methoxy-trityl-3'-O'2-cyanoethyl-N,N-diisopropyl!phosphoramidite-2'-deozy-β-D-erythro-pentofuranosyl-imidazole-4-carboxamide

In a manner as per Example 29, the compound methyl5-(cyanomethyl)-1-(2'-deoxy-3,5-di-O-p-toluoyl-β-D-erythro-pentofuranosyl)imidazole -4-carboxylate can be treated with 2-(3-bromopropyl)anthraceneinstead of iodononane. After work-up as per Example 29 the product canbe treated as per Examples 35 and 39 to yield 5-(Cyano anthracen-2-yl(propyl)!methyl)-1-(5'-O-di-methoxy-trityl-3'-O'(2-cyanoethyl-N,N-diisopropyl)phosphoramidite-2'-deoxy-β-D-erythro-pentofuranosyl-imidazole-4-carboxamide.

What is claimed is:
 1. A method for preparing a 3-deazapurine nucleosidecomprising the steps of:a. alkylating acyano-1-(3,5-di-O-p-toluoyl-β-D-pentose) imidazole in the presence of abase, said alkylating agent having the formula RX, wherein R is alkylhaving up to about 12 carbon atoms, alkenyl having up to about 12 carbonatoms, or aralkyl having from about 6 to about 30 carbon atoms; and X isa leaving group; b. ammonolyating the alkylated cyanoimidazole; and c.cyclizing the ammonylated cyanoimidazole through basic catalysis at atemperature of greater than 90° C.
 2. The method of claim 1 wherein theleaving group is a halogen.
 3. The method of claim 1 wherein thecyclization is performed at about 95° C.
 4. A method for preparing a3-deazapurine comprising the steps of:a. providing an alkylcyanoimidazole carboxylate; b. alkylating the alkyl cyanoimidazolecarboxylate alpha to the cyano group in the presence of a base, saidalkylating agent having the formula RX, wherein R is alkyl having up toabout 12 carbon atoms, alkenyl having up to about 12 carbon atoms, orarylalkyl having from about 6 to about 30 carbon atoms; and X is aleaving group; c. ammonolyating the alkylated cyanoimidazolecarboxylate; and d. cyclizing the ammonolyated cyanoimidazolecarboxamide through basic catalysis at a temperature of about 75° C. 5.The method of claim 4 wherein the leaving group is a halogen.
 6. Themethod of claim 4 further comprising the step of protecting thecyanoimidazole carboxylate with a protecting group therefore.
 7. Themethod of claim 6 wherein said protecting group is tetrahydropyranyl. 8.The method of claim 7 further comprising the step of acidifying thereaction mixture containing the cyanoimidazole carboxylate to remove theprotecting groups.